My opinion? Try 'em all out. The ability to switch up is why druids rock. Between 70 and 80, I spent 6 levels as feral, 2 as moonkin, and 1 as resto just to keep my skills up and try out the new talents.
Stockpile gear for alternate specs if you can (while not taking it from people who need it more for their main specs), and re-spec whenever you get the urge. If you have to run a few instances in sub-par gear, it probably won't matter all that much anyway.
Running as feral/tank helps you appreciate the job of a healer much more, and vice-versa. Druids are in a unique position to be on both sides of that one.
Moonkin/balance is fun, and very reasonable for PvE content. You should try it out for sure. Playing moonkin for PvP will teach you things about kiting and rooting that you don't necessarily learn as feral, but will nonetheless help out your feral game as well.
So yeah. Do it! If even just for a few levels.