Guess I've been lucky, I haven't had any problem at all watching HBOGo via my xbox and through PlayOn. I'm on 12MB AT&T u-verse ADSL, the computer and consoles are on a gigabit internal network.
I've watched several episodes of Ricky Gervais, several movies, and a few of the comedy offerings, and never had a buffering issue of any sort. Also, everything looks fine on my 62" tv, but i'm admittedly not AS picky about picture quality because i understand the limitations that come with streaming.
i'm a big advocate of PlayOn, it's well worth the lifetime subscription fee. It's updated fairly frequently, and they're always adding new features. I like being able to pick up feeds from most of the major networks if my DVR misses a show I want to see, and it's a great way to watch Hulu on my TV for those items that are not included in Hulu Plus.
I don't know if the PS3 will ever get a native app, sometimes I think Sony doesn't know what to do with their console this far into its product life. By contrast, Microsoft made a decision to transition from an emphasis on gaming to an emphasis on media, which is why so much great content is appearing there first.