I did, err, do have FIOS.

Phone service was fine. I couldn't tell any difference from the copper phone line it replaced. Eventually dropped the home phone due to lack of use.

Internet service is fine. I have the lowest speed package they offer - think it's 5/2. Never an outage in (I'm guessing here) 4 years, never seems slow, have never needed to call for support.

Cable TV was a mixed bag. The service was never down, picture quality is great, channel changes are instant (unlike u-verse, apparently). On the other hand, their proprietary DVR was horrible - buggy, lousy user interface, search function would bring up channels you didn't receive, etc. I cancelled the service, partly because of the lousy DVR, mostly because I just don't watch much TV - I was paying about $10/hour for cable TV, based on how many hours/month I watched it.

Never had a problem with billing/administrative. They sent the bills, the bills were correct and ontime, I paid them, no issues.