Ive been wishing for this EXACT thing for ages! Straight forward, accurate ports of the DD1 & DD2 arcade games and thats exactly what this app delivers. (DD3 was never that great, but the app is more than worth the price of admission for 1 & 2 alone.)
One thing about DD2 though, (aside seeming easier than the original arcade game... which might just be my memory failing me)
When you get to the final fight (spoiler) with your evil twin(s), and have the music set to the original 8-bit soundtrack, the wrong song plays during the fight. What you hear in this version during the fight is only MEANT to be heard during the shadow twins appearance. During the actual fight youre supposed to hear a similar, but markedly different theme. (It should be the same track that "wicked god" from the arranged soundtrack is based on.)
Also, during that same appearance scene, the app plays a sort of Victory jingle that is not meant to be heard (it exists in the arcade games rom as unused data, it was never heard at any point in the game originally.)
These are just minor points... Im trying to help you keep it as accurate as possible since Ive always loved these games!
Bimmy Lee about Double Dragon Trilogy, v1.1