In general, TiVo seems to work best on FIOS. The Roamio/Minis will work exactly the same with FIOS as they do with your cable company, and not having to deal with a tuning adapter is a big advantage in my book. If I had the option of FIOS in my area, I'd drop Time Warner so fast their heads would spin. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.