Most LA+HD creatures aren't that bad on the level they could first enter the game, although ones whose power is just a lot of 1/day abilities might be kind of annoying. The real problem is that they start to get weak very, very fast, especially if you go into any class with abilities that have a power curve (like, say, any spellcaster.) At higher levels, you're left with a bunch of obsolete abilities from your race, and a bunch of crippled powers from your class... few high-LA races have abilities that can synergize with the class in a useful enough fashion to be worth taking.

In other words: In a game without much optimization, even high-LA creatures are fine -- as long as the game starts at their ECL and doesn't go for very many levels after that. But for an extended game, even one with no optimization at all, anyone playing a high-LA creature is probably going to get frustrated very quickly.