No, none of that has to do with the controller (I only mentioned the 88 thingy because you seemed so all fired purist about nothing feeling right to you ). Your computer sounds about right for running Ivory (don't know if it Vista ready yet, though... you got a XP partition?). I would use a second HD for streaming Ivory, though, and just about any streamed stuff... they don't like to work off your audio HD or system HD if you are using a DAW and streaming VSTi's at the same time (should be OK with two HDs if you aren't recording audio while Ivory streams).

But obviously, playing real piano sets on a plastic keyboard, no matter HOW good, is a compromise, and adds to the 'unrealism' of it while you are playing.

But put that aside, and playback should make you smile... if not DURING the performance!