Carbon has a greater strength (and stiffness) to weight ratio than aluminum does, and is typically used for aerodynamic road rims, as the idea is to have deep sections with lots of surface area to generate lift (like an airplane wing). An 80 mm deep aluminum rim would weigh more than a complete set of XC wheels, but in carbon, is a reasonable 595 grams. For mountain bike purposes, the same rim that is a trail-worthy 35 mm width (and very stiff as well) weighs as much as a typical XC rim, if it is made of carbon rather than aluminum.
Weight, stiffness, and strength, that is the "Holy Grail" of vehicle performance, but it comes at a price, and that price is in dollars and cents. The design and layup of advanced materials have come to the point that the carbon rim is a viable choice for mountain bike use, but the initial cost (and replacement) of what is an imperiled component (nothing is indestructible) is many times the price for an aluminum equivalent. A carbon wheel is typically twice the price of an aluminum wheel, and would be more than five times the expenditure to replace the rim only. The old saying goes "speed costs money...how fast do you want to go?".
So what does a carbon wheel ride like? One might think that something "as stiff as a board" might feel dead and harsh over the bumps, but it's simply not true. A board is an appropriate comparison, as wood is like "nature's composite" and has a natural damping of high frequency vibrations. I could best describe this sensation as "organic". To give the carbon rim more springiness, a lighter spoke gauge is used, saving weight while isolating harshness. The extra stiffness though, is most welcome in steering response and power transfer.
The same rider that shells out the extra thousand or so dollars for a carbon frame can expect an even greater benefit from a set of well designed and constructed carbon wheels. But I can't really say that they are the ultimate cost effective solution.
Most riders that use tubeless tires do so in order to run sealant, staving off the constant flats in areas of thorny plants or cactus. Here in the Sonoran desert, tubeless tires are very popular despite the hassle of maintenance and setup that comes with them. When almost every ride finishes with a flat tire (with tubes), tubeless is far easier to deal with. Sure, one can fill their tubes with "Slime" but that can get heavy, and does nothing to reduce the possibility of "pinch-flats".
Another advantage of tubeless is weight savings, though it's not as much as you would think. Some tubeless tires weigh the same as a tube tire with a tube, so with an ounce of sealant, will actually weigh more. However, most "tubeless-ready" tires (tubeless tires that don't hold air without the sealant) weigh about the same as tube tires, and most tube tires can be run as tubeless (with the bead strength and stiffness equal to tubeless). To this, you only have to add 100 grams of sealant (two scoops of Stan's), compared to 150-200 grams for a decent tube. Not a big weight savings, but if you are counting the grams on every other component, a worthwhile pursuit.
The other advantage of eliminating a tube is rolling resistance. The sealant is liquid and has no "internal friction" against the tire (at the contact patch the tire deforms and the tube must slide against the inside of the casing to conform to the dynamically changing shape of the tire). For an endurance or XC racer, this can save a few seconds per hour of racing. Also, some report that the tubeless setup has a more supple feel that can give a bit more traction, that and the possibility of running a few less pounds of air in the tire will improve the handling.
All that being said, my advice is "If you don't need it, I wouldn't bother." Never has an advancement added more difficulty for such a basic and necessary maintenance issue (it is often necessary to use an air tank or CO2 canister to initially inflate a tubeless setup). Almost all of us have to fix our own tires and you will experience a steep learning curve in order to work with tubeless effectively. I would suggest that you watch as many videos showing how to install tubeless tires as you can. It may be awkward at first, but will get easier with practice.
Also, you'll have to carry spare tubes anyway, since the leak may be too big for the sealant to fix. Sealant eventually dries out and you must replenish it every couple of months or more, so you may want to carry a small bottle with you. If you are a rider who likes to switch tires according to the terrain, then tubes are much easier.
Back in the early '90s there were few cassette type rear hubs, Shimano, White, Hugi, and a few others that used a Shimano sprocket body. No one talked about points of engagement or ratchet speed on these hubs or the many freewheels that were available at the time. Mountain bike technology was in its infancy and new, lower gears became necessary. That's when Chris King developed his patented "Ring-Drive" ratchet hub. With 72 points of engagement, it was more than twice as quick as the next quickest White Industry at 24 points. A whole new category of feature was born.
So, who needs a quick ratchet? The lower the gear and the slower the overall speed, the more a quicker ratchet comes into play (pun intended). If a ratchet has 18 points of contact, that number is divided into 360 and produces a maximum of 20 degrees until the ratchet engages. (It is possible that, by chance, a rider starts to pedal exactly when the ratchet makes a "click" and engages in that instant, in 0 degrees.) A lower gear means that the pedal rotation is a greater percentage of the rotation of the wheel and more distance for the pedal to catch. In the case of a road bike at high speed, there's only a fraction of the difference in ratcheting speed than there is for a mountain bike plonking around in a rock garden, requiring short jabs at the pedal stroke to maintain momentum.
I have yet to hear a road biker complain about a slow ratchet, but the question is a hot topic on the mountain bike side of things. King has established the bar for quick response (5 degrees), but even that has been surpassed by some. Industry-9 is 3 degrees and Kappius is only 1.5 degrees, which is twice as quick as the Industry 9 and over three times quicker than King. But remember, we're only talking a few degrees overall. Not wanting to be left behind, Shimano and DT have upgraded their higher model hubs from 20 degree to 10 degree.
How do you decide the importance of ratchet speed for yourself? Try to determine the number of engagement points on your hub by holding the cranks steady and counting the clicks you hear as you rotate the wheel one revolution (hopefully you can hear them). If you often feel an annoying clunk as you go from coasting to pedaling then you will want more engagement points than your present hub. An efficient pedaler may not need as quick of a ratchet as a chunky pedaler, since they smoothly accelerate their legs in order to catch up to the ratchet without a clunk.
Really fast ratchets sound more like a fishing reel than a bicycle, and some riders have even complained that their ratchet isn't loud enough. Personally, I remember going on the first ride on my new King hub (coming from an American Classic at 24 engagement points) and rode for half an hour before remembering "Oh yeah, I have a new wheel," but then, I'm a pretty smooth pedaler.
Dave is definitely an awesome wheelbuilder! His customer service is also great. I especially like that he takes the time to discuss your bike, your weight, and your riding style so that he can build the perfect wheelset!! I noticed a huge performance increase as soon as I installed my wheelset from Dave. ~ psinsyd from mtbr.com