coming from a guitar player, I spent some time looking for a good pno emulation too at one time. I got the free 4font module that has zero adjustments, but was the only freebie I could find.... this was about a year ago.
I demo'd the rest of the True Piano stuff and thought it was great. The freebie worked for me (along with Dimension Pro which I have also...came with Sonar PE) so I didn't shell out any $$ to get any better.
There's actually a "shootout" in the Sonar forums, but I think the style of music has as much in the decision as anything else, not to mention once it's in a mix....
The TruePno is a VERY low CPU load, making it ideal for live work too.