One of the best free pianos around, probably better than many commercial piano plugins or sample libraries.
Sound - it has an excellent open and clear sound. Many modeled pianos miss a certain "brilliance" of the sound as well as some sampled pianos (probably recorded with darker microphones). This one sound like a real good piano, how you would hear it from near (while playing on a real piano).
Interface - a simple interface with very self explanatory controls. You can tweak the sound, add some impulse based reverb, open/ close the lid, control dynamic response (velocity curve), etc...
CPU and RAM usage - as mentioned by developer, low usage of both. Can run on slower or older computers without chocking your projects.
On the downside:
- the release is a little unrealistic and can be a turn off for people who are used to play real pianos. You can fix it a little with the release slider, but not make it good. In a project you can hide the problem by using the sustain pedal. Still, if you care more about the sound than response, this is the free piano you'll ever need.
- interface could use a more inspiring design/ colors/ better knobs and sliders graphics.