Personally, I would not be willing to wait until after the eighth gym for a team member, but Salamence is one of the better pseudo-legendaries. Obviously, it's stat total comes out to being 600. It has great attacking stats, good speed and alright defenses with a nice HP stat. It depends on what you want. I like to grow bonds with my team, so before the seventh gym my team is closed, but Salamence is a really great Pokémon. Some other good flyers could be Swellow and Altaria (with Altarianite of course). For the later section of the game, you don't even need a flyer on your team as you can use Latias/os without it even being in your party. But like Stakatacool said, it would take forever to level up seeing that you get Bagon in the thirties (I think). If you don't mind waiting forever for a Pokémon and then needing to train it up about twenty levels for it to be effective, go for it. If you just want a Pokémon that will destroy the Pokémon League (except for Glacia if Flamethower doesn't OHKO) and don't mind such a long wait, definitely. Oops, a bit too long!