I bought the Roamio Plus and one Mini and we love it. No issues with Fios.
I have one thing that Tivo should change. Right now, if the Roamio is recording suggestions and all tuners are occupied, it will not let the Mini watch live TV. I know I could turn suggestions off to avoid this problem, but we like the suggestions feature. My wife will be confused because the Mini will tell her all 6 tuners are occupied and she cannot watch live TV. Upon investigation, on each occasion, the Tivo was recording several suggestions. I think that if a Mini attempts to watch live TV, it should cancel one of the suggestions.
I know one solution is to record the show she wants to watch, but this shouldn't be necessary.
I love the Tivo otherwise.