I love the addition of a wild card team. I don't think it waters down the playoff system at all. In my opinion it almost brings baseball back to its roots and the importance of winning the division. Imagine the Red Sox and Yankees are battling for first place both with 95+ wins. In past years, the teams might have put more stock in going to the playoffs healthy. This will drive both teams to desperately try to win eliminating the chance of having a 1 game series with Tampa Bay, Toronto or whoever (which would be totally terrifying and exciting.) It also gives the smaller market teams almost an insurance that they have a chance every year. In the AL it is almost assured that they Yankees and Red Sox will make the playoffs (the last 2 years have been mainly a fluke, IMO) or have a incredibly great chance baring horrible injuries. I think this energizes these smaller market teams, and in the long run makes the MLB a much better league.
As far as inter league play goes. I am actually warming up this idea. I don't think it's going to be as drastic as people think. I'm sure for most of the season there will be only one series going on at a time. I've heard it will increase the amount of interleague games from 18 to 30. It's a big change, but perhaps a welcome one?