Found that mine was a bit slow off the line, too. I could rev it up, but as I let the clutch out the revs would drop and it would bog if I wasn't enthusiastic!
I got it a lot better, right up until the oil line came off and it seized
What I recommend doing is checking your power valves are set as per the HRC method outlined on the tuning part of the site. That should make things a lot better if it is out, don't rely on the marks on the butterflies that the power valve cables attach to. That's where I'd start.
I did that, and tweaked with my jetting a bit and the bike was awesome! Though, start there before you go fiddling with jetting, and if you do jet, be very careful. Do make sure those damn oil lines don't slip off... I'm going to use better clamps (and a LOT more caution) despite what Andy says.
Apart from that, sounds like a typical NSR, rev it, let the clutch out, wheel stand. It's a blast.