I don't think the GTS is too bad if you're only looking for really easily obtainable Pokemon, or ones that aren't really in high demand. I've gotten all my version exclusive pokemon off the GTS, without much issue. I do wish you could specify that you exclusively want Pokemon with a certain item/trait though. Like, I'd like to be able to say I want a Magmar holding a Magmarizer in exchange for whatever Pokemon I put up. I know you can ask in the text box thing, but people aren't necessarily going to bother. A couple of times I've also misinterpreted the text - I thought someone was offering a Pokemon with Pokerus, but it turned out they were asking for one with Pokerus. :/
But yeah, it's definitely overrun with people asking for completely unreasonable trades, and it could use some work.
But yeah, it's definitely overrun with people asking for completely unreasonable trades, and it could use some work.