EWQL's new piano library is high on my shopping list. At ~260Gb(!), it might be overkill, but as a piano player, I find it very exciting to have that much depth in a sampled instrument.
Synthology Ivory and Galaxy II Grand Piano are a couple other great options.
Right now I'm just using my Yamaha S90 for piano sounds. Throw on a good IR reverb, and it sounds pretty decent.