It's excellent. Looks great on my computer, looks almost like an HDTV channel when I watch it on my PS3 with my TV. The PIP feature is great, too, as is the player tracking feature if you play fantasy baseball (tells you when your selected players are in the hole, on deck, hitting or pitching).
I dont know about the video one, but my friend has the radio one which is really cheap and it is awesome. Any game live from either team's announcers from internet or any smartphone (has to have 3G I think). 5 by 5 quality.
On that note, the video subscription also gets you radio broadcasts. While that typically doesn't matter since you have video, it does matter for local games since you won't get video of those (e.g., can't get Rangers or Astros games if you live in Houston).
MLB.TV is absolutely fantastic. Once you download the HD plug in, the quality is just amazing. I really love what the NBA and MLB have done with their on line services. Just amazing. I wish the EPL would do something like this. They would make a fortune. Not to mention what the NFL could make.