I'm very suspicious of this and related products. The thing that's really great about all our acoustic musical instruments is that when you push on them, they push back . I don't mean this simply in the normal force sense. Consider a guitar. You've got a string which you press over a fret with your left hand. This can be naively emulated by a switch. But with the guitar, the timber and pitch change depending on how y…
I agree that keyboard instruments are the most convincing, and certainly the easiest virtual instruments to play (since playing a digital piano is the same as playing an acoustic piano), but there are some pretty expressive and convincing virtual instruments out there:
Bass guitar (acoustic and electric): http://www.spectrasonics.net/products/trilian-audio.php
Drums: http://www.toontrack.com/products.asp?item=30
Acoustic guitar: http://www.youtube.com/watch?feature=player_embedded&v=q...
Electric guitar: http://www.vir2.com/instruments/electri6ity
Orchestra (perhaps not the best solo instruments, but pretty great results for a whole symphony): http://www.vsl.co.at/en/67/702/703/413.htm and http://www.soundsonline.com/Symphonic-Orchestra and http://www.garritan.com/products/personal-orchestra-4/
And, just to mention it, the best piano virtual instrument I've heard so far: http://www.synthogy.com/demos/grandpiano.html