I'm working in 24/96, and while I don't use cubase, I'm not having any real probs working at that resolution. (I run many tracks, and lots of heavy duty vst plugins.)
I'll have to dig it up, but there was a great debate on here about the differences between using 24/48 and 24/96 and it got quite heated, however at the end of the road, with computing power being so dirt cheap these days, they didn't make any compelling arguments *not* to record at 24/96, so that's what I do.
-N