Having used only Shimano for 20+ years, I bought a HT off here a few years ago that was equipped with as new 3x9 X0 shifter's and rear mech, front mech is an XTR, sram cassette and chain, with a RF crank. I immediately liked it's positivity and instant shifting. It's my winter bike and with minimal maintenance, it has been reliable and precise; spring time cleaning includes clean and lube of the cables.
I do like the subtlety of XTR and the lightness of XT, however, I felt both could also feel a bit vague and I needed to fettle a lot more to keep them shifting when I wanted to shift.
I specced and built my new FS, bought in May this year, runs X9 3x10 shifter's mech's, chain and cassette, with SLX cranks. It too is performing faultlessly; whilst I find it not as 'solidly precise' as the X0, it's lighter lever action is still very positive and accurate and like the X0, handles multiple shifts with no fuss.
My current project Ala Carte, is being done with an attempt to control expense, so I'm hunting ebay, here and STW et al for used X9/X0. I'm converted!!
Personally, I have more confidence that the gear I want will be delivered with the Sram higher end stuff than I do/did with XT and XTR shifters and mechs.
Enjoy your build!