The original ReBirth on PC was my first music app, so I have a lot of nostalgia for this one. When I loaded it up and saw the classic demo song, Alloy Cowboy, I was so very happy. This has a lot going for it, including many of the features I wish technoBox2 had, but it isn't quite as easy to use. The knobs are small and there is no way to resize the screen.
As of update 1.3, CoreMIDI and Background Audio have been added to ReBirth, along with a fun Duo mode for playing with a friend on the same iPad.
While it has a great sound, the cumbersome knobs make it hard to recommend what should be a performance oriented app. Beginners are better off with technoBox2 and experts are better off with bleep!BOX or rolling their own techno bundle with something like Bassline for a synth and Molten or MoDrum on drums; all of which will play together with CoreMIDI!