Personally, I don't like using them, and I prefer it when other people don't. It ruins the creativity of the game. there's 650+ pokemon in the game for a reason, not just the legendaries. But it's more the fact that from another angle, I like to say to myself, "Is it really possible for, say, 600 trainers to ALL have Lugia?" It doesn't make sense. at least this way, you can tell a story. Thats my opinion, though. Some of them, like Celebi, however, can likely be used by multiple trainers, so they aren't so bad. But when you see fourty guys weilding a Zekrom/Arceus/Groudon, I think it's kind of unbelieveable.