I agree. i don't care for them much at all. the concept behind them, however, is awesome. to be able to use a certain pokemon, as a completely different type. but, the whole metal thing just.. sucks.
Aside from that, as someone already mentioned, they only work well together. aside from a few combos, the delta pokemon only work well with other delta pokemon, where-as pokemon from other sets are straight-up as they are, and have good powers/bodies/attacks that can be comboed with nearly anything. but, theyre making the cards now so that you HAVE to play an entire deck of delta pokemon in order for the combos to work. and quite frankly, with the exception of one or two of them, the delta pokemon as a whole are extremely weak. none of them hit really heavy, and the ones who do takes a lot to do, or has a heavy consequence (mainly being discarding)
As a whole, i hate the delta pokemon, with the exception of a few. But, they really need to focus more on making the cards more openly playable, and get away from the constrictions of having to play an ALL delta deck in order to make them work.