I’ve built four bikes with SRAM, two with Shimano. I’ve only had an issue with one SRAM rear mech – a 2009 X9 that stuck in 1st or refused to go into 9th. The other stuff has worked fine, shifters have been perfect and I’ve been very happy, so much so that I just shelled out for X9 2 x 10.
The XT stuff on the other bikes has been fine, too, apart from a really stupid design on XT shifters that allows a loose cable to be taken round the inside of the shifter, requiring a complete rebuild of the shifter (very fiddly) to get it out.
But I really cannot understand how SRAM can charge, on average, an additional £50 per item compared to a similar quality Shimano part. My X9 2×10 cranks were heavily discounted at £177 from an RRP of £289. They’re no better than XT but cost so much more.