I have now bought ELITE and think it is the best software out there for instrument practice. RANT is cool to start with, but once you know what to do with the instruments its usefulness falls rapidly. FS2002/4 is OK but like X-Plane is much too finicky, pinickity and annoying to be useful. ELITE is about as close to practicing like you fly that you are likely to get without speding !!!!! loads. It even works on a basic machine. Price is about £80 for the 172/Archer version now I think (recent price slash). Their email support is very good too.
www.flyelite.ch.