Stans NoTubes done well with the right rim/tire combo and alignment of the planets (I use Stans rims, so no probs there) is a good system. The only real issues is with 'burping', which is where you run too low a pressure and hit a bump and the tire temperarily dislodges from the rim.

From all accounts (Net reviews, dewds at the LBS) tubeless with Stans is good. A PITA, but good.

Mavic's tubeless on the otherhand is a bit different. The tires themselves have to have a massive bead and the sidewalls have to be airtight, so UST tires tend to weigh a ton. The only reason to go with Mavics system is convenience.

If you take two examples, a front Crossmax UST with Python New Gen UST tire and sealant, vs a nice handbuilt front wheel (eg: Tune hub laced via DT Super Comps to Stans ZTR Olympic rims), a Stans strip and sealant, the latter, while not as convenient as a Crossmax weights.....brace yourself....282g LESS than the Crossmax UST.

Thats an instant half a kilo off the weight of your bike, with no extra dollars out of your pocket.

Maybe that's why the guys on the mtb forum reckon tubeless is a joke, or is it because they're all hucksters?