FWIW -
I've been using my iPad 2 with MIDI Designer Pro on an Alesis iO Dock for quite a while, and it works GREAT! I'm using the combination to build some templates for some of my Moog hardware, and so far it seems like everything is working correctly and as advertised!
To caveat, I have not tried anything that requires sending or receiving SYSEX data, but CC, program change, and note commands all seem to be working just fine.
Keep in mind that as long as you have a compatible iPad, the iO Dock is going to give you conventional MIDI DIN, MIDI USB, and combination 1/4"/TRS audio I/O, and it charges the iPad while in use. And the price has come WAY down in recent months!
As an alternative, if you still want a robust MIDI connection that works quite well, you might think about the iConnect MIDI. Doesn't offer audio and doesn't charge connected devices, but it is a cool way to link together several DIN and USB MIDI devices with your iOS gear.
UPDATE 24 July:
Unfortunately, I can confirm that the iO Dock does NOT work with SYSEX with ANY app! That's really a shame, because other than that HUGE oversight on the part of Alesis, the iO Dock really is a great way to integrate an iPad into the studio...