I recently bought this great virtual instrument/keyboard after trying the free version. The free version gives the sound of a studio grand (Steinway Model D) and lets you play around with a few of the many samplings. The full version has modern upright (Yamaha U3) and Fender Rhodes Mark electric piano settings. I'm pretty sure that once you try Addictive Keys, you'll want it for yourself – hence the name. Highlights include the intuitive interface, quick loading time, and a variety of effects.
Give Addictive Keys a whirl.