My HD's running X0 now throughout, it's strong, light and looks a million $. I moved from XTR sometime ago on the majority of parts as I couldn't match the reliability of crisp shifting when comparing to the XTR on my other bike. I've no experience of SRAM X0 chainsets though, but do run a SRAM chainset in the form of a Truvativ Noir on my hardtail. For me, the XTR chainsets take some beating for slickness of shifting, but it's not pretty looking at the cost and even less pretty to cost out a replacement set of rings.... $$$
I haven't tried the latest gen of XTR but until XX, X0 was always completely up there (better IMHO) with XTR.
Go SRAM, if u look smart and aren't bothered about having 10x setup, you can get previous gen X0 for cheap now and it's superb.
Happy trails on the HD, great choice of ride
