Yeah, I just can't understand why they went back to freewheels and friction shifters. Oh wait, wrong 10 speed....

In all seriousness, like 9 speed, when it's set up right it works great, when it isn't setup right, the experience will absolutely suck.

With the sram vs shimano thing, it is still the same as it was with 9 speed. A sram rear deraillieur won't work with a shimano shifter and vice versa.

The first version of 10 speed shimano won't work with the new 10 speed shimano stuff.

The 771-10 series XT, 770-10 XT won't work with the new 780 series XT (dyna-sys) The cable pull is different.

In theory you aren't really losing anything. On a fully geared bike there are gear combos that are a no go. With a double up front 2x10, you lost a chainring up front, but got an extra cog on the back. There is a 3x10 option, but I have hardly ever heard of anyone wanting that option, the doubles sell more than the triples I guess.

I've tried a couple of bikes with the 10 speed drivetrains, one with sram(XO), the other with shimano(XT). To me, the sram offering felt a bit cheap at the triggers, where I thought the shimano triggers felt better. Durability: Shimano easily, I've seen sram shifters come new out of the box and be broken. Shimano's shadow plus deraillieur with the adjustable friction is being viewed as a game changer. There are also some advantages to the sram stuff. The match maker is brilliant, if you have a busted chain you don't have to hope that your lbs has the correct 10 speed shimano chain, the 10 speed sram chains are the same between the road and mtb. The shimano 10 speed chain for mtb is different than their 10speed road chain. The biggest advantage for Sram is that their 10 speed mtb shifters are compatible with any of their 10 speed mtb deraillieurs.

While to be honest, I don't ever see myself having a bike with a 10 speed cassette, let alone 9 anymore.