i have an nr90 (a green one) , may be previous to the gr2 and it works a treat. just got it out of the shed this week after a year or two, charged the battery, give the gas can a few taps and shakes and away we went.
IIRC the battery goes flat if you leave it in the gun (i think the flashing green light does not stop so eventually drains the battery) apart from that, no problems.
I have the NR90 GC2 - the clipped head version which is compatible with paslode nails and gas so they are readily available. Gun works as well as any gas nailer, that is to say if the weather is cold and you are working outside you will probably be at the very least tempted to throw it in a skip. As long as you get reasonable quality gas and make sure it is in date, you should be ok. When I had a technical problem with mine, Hitachi were helpful in sorting it out over the phone.
Thanks for your endorsements chaps. Managed to get an NR 90 GR2 at a fantastic price (new) and couldn't be more pleased thus far. 20 degree round head nails freely available from a number of suppliers at a good price - as is compatible gas. The build quality does look awfully good.