The timer isn't that bad, because it gives you 20 minutes per deckbuilding phase (broken up into 7 minute, 7 minute, and 6 minute chunks). Usually when games have real-time play, it's designed to be hectic, but I feel MB gives you just enough time to make strategic decisions at a relaxed pace (with no down time and being engaged 100% of the time!), but actually moving the game along and not falling into analysis paralysis. It's the first time I've ever seen a game do that (real-time, but not rushed) and I'd really like to see more games like that.
I've played the game quite a few times now, and it's definitely in my top favorite games. There's also a co-op mode in the Set Rotation expansion that can be played solo, and it's a pretty solid way to play it.