I also get Comcast Sports Net in HD with FIOS...at the beginning of last season, they only had Celtics home games in HD but that issue has been resolved. When I first got FIOS I had some cable box lag/connection issues, but we got the faulty boxes replaced and haven't had a problem since.
I would have hoped they added NBA TV by now (they already added NHL, NFL, and MLB networks, so I am not sure what the holdup is). They do have so many more HD channels compared to Comcast, so while Comcast commercials hype their OnDemand selection (which admittedly is much better than Fios), their HD channel lineup pales in comparison to Fios. Especially the number of premium HD movie channels available.
Unfortunately, this is a moot point for me, I am moving from the suburbs to Brighton next week which means no more Fios for me

I would recommend Fios to anyone, but I admit I am not a huge OnDemand person, which could be an issue. Also, their menu looks like an Atari game compared to Verizon's menu. But at least I finally can see NBA TV.