My team also recently built a chat service into a mobile app for a cruise line, and had to have high resiliency to network drops and offline users - while having a mission-critical "guaranteed delivery" requirement. We also chose OpenFire since it was an off-the-shelf XMPP server, and (presumably) was easily extensibile via plugins.

After working with (hacking around) OpenFire for two years, I 100% agree with your statement. The clustering plugin routinely fails (to the point where we have actually investigated not even clustering it anymore), the admin interface routinely displays "wrong" data, and other fun bugs we found along the way.

Does it work for us (with a lot of client XEPs and additional custom plugins)? Yes, it does an acceptable job. Would I choose the same product again, if given the choice? No.