I am currently trying to get a refund from MLB.tv. Don't believe the ads that say, "Watch all the games on your favorite device". I have all the requirements needed to watch games. I have an HTC phone with Android 2.2. They are now saying this phone will not be supported. Also the tablet I have was just able to get games.
If you want to go to MLB.tv, go to their support forums and make sure your "Favorite Device" can actually do everything they promise.
I have a Roku and have had a bad problem with rebuffering. The Panasonic Smart tv I have doesn't have any of the extras they promised, such as watching 2 or 4 games at once. They didn't tell me thayt until AFTER the date I could get a refund. My internet download speed is a consistent 8 Mps. The minimum they require is only 3 Mps, but it still rebuffers at least once an inning.
Some people have had a lot of luck, hope you do too!
Sorry you've had problems with MLB.TV. I've had absolutely no rebuffing issues on my PS3; the Roku isn't quite as good. No rebuffing, but sometimes the picture goes to what looks like wide-screen SD for a second or two before switching back to HD. Even in HD the PQ on the Roku isn't as good as on the PS3.
The PS3 was actually a really good investment for me; not only does it play games, but it doubles as a great blu-ray player and it's a gateway to Hulu plus the NHL, MLB and (this fall) NFL Sunday Ticket.
Good luck in getting your refund from MLB.TV.