I am an Astros fan, so keep that in mind.
I've always thought playing in the only 6-team division was a clear disadvantage, particularly when the AL-West only has 4. That being said, I wouldn't want the Astros to be ones to leave. I've always felt the Brewers should go back where they came from.
I could probably get used to it, but I've long enjoyed hating the Cardinals and Braves. I know Houston doesn't have the highest profile rivalries or the most tradition, but as an Astros fan I would be a little bit sad to be leaving the NL. Taking the league as a whole, though, it probably makes sense and would be good for the Astros long-term success. It would just take a lot of getting used to.
I'm okay with year-long interleague play, but interleague play has been around for almost as long as I've been a semi-knowledgeable baseball fan. It always seemed weird to me that it didn't always exist, since every other pro sport has it, but I understand why that's attractive to old school baseball fans.
ETA: I do like the idea of a division or at least league rivalry with Texas. That would be fun.