Just beat the game...it really started getting irritating after a while. The regular Abobo/O'Hara enemies become annoying, since they block a lot of your hits, inflict a ton of damage, and swarm you relentlessly when you're on the ground. There's no real good way to avoid being crowded by enemies, and it takes forever to turn around, leaving you open to hits from behind constantly (unless you've mastered perfect guard, but it's still tricky in crowds). The jump over the toxic pit at the start of one of the middle missions is just bizarre and confusing, and the camera shifts guarantee you'll fall to your death a fair handful of times before figuring it out.
I did like parts of the presentation, though. Enemies from both the arcade and NES versions were represented well. The boss hideout and the portrayal of Willy are both pretty cool. I kind of appreciated the attempt to give more detail to the original story. I liked how they sort of explained the origin of the final boss, although including the Mysterious Warrior fight from the NES version could've been a nice surprise for the very end.
Oh well. I could see myself trying to play it again one of these days. Definitely not for anyone who isn't a big Double Dragon fan, unfortunately.
...but! I just recently found out that the iPhone Double Dragon was ported to Android. Woohoo! I've been playing the hell out of that one lately.