We've tested IN2AR, ARToolkit Wikitude, and Vuforia in our office, most via Unity (because of lack of up-to-date AR options in AIR).
Vuforia is notably more responsive and reliable than any of the other options and their latest release can make use of VuMark's which seem to be a little more reliable again on mobile devices and allows for near identical markers triggering different content.
The downside to Vuforia is it's expense per app.
Interestingly, ARToolkit seems to be getting actively developed again. We tested this recently and it seemed fairly comparable to Wikitude in terms of performance. ARToolkit v6 is due for release soon, so I'm hopeful it'll improve again.
If Wikitude is presenting roadblocks, perhaps ARToolkit is worth a look. It's licensed under LGPLv3. I attempted to understand what implications that would have for commercial projects, but the legal jargon was too much for me. From what I've read so far, LGPLv3 is supposedly more compatible with non-free licenses...?