This is a recent review I made on the TUSA IQ-850 VIBRATING Dive Computer. Like others said, best to pay attention, but as I found out, it's human to error; better to be safe than sorry. Plus, the IQ-850 allows you to set reminders, limits, etc that are very useful in your dive. Why wait until you hit the limits to be warned and take action.
Review on LP website:
I have Tinnitus and can't hear high frequency audible alarms very well. I actually went into DECO because of this on a Suunto (I was on air and the others on Nitrox...no one knew and I was so busy taking pictures I relied on the DM and other divers. Fortunately it was the first dive and there was no DC sickness. Lesson learned: take care of myself and not rely on others). The IQ-850 has a vibrating alarm and notification system like on a cell phone that works really well; I can easily feel it through my wetsuit sleeve. No more divers looking around to see who's alarm is going off. I can now notice my reminders and warnings in silence. 

I'll soon get the USB software transfer system now that I've successfully installed Parallels and W7 on my Mac (only used 10GB memory). It's really the only option and solution for Mac. Unlike the other user who had so much trouble with his IQ-850, mine has been flawless over 60 dives and a year of use. The only issue I've had is the display light on mine is very poor, I'm unable to light up the display on a night dive. Apparently this was a known issue on a certain batch of IQ-850's. Now that I'm home I've contacted TUSA on the matter and they said it's a known issue and to send it in to repair/exchange. They responded within hours and issued me an RMA; excellent customer service in my opinion. 

It's human to error and if you can't hear the alarms, it limits the use of a DC. If you have Tinnitus or hearing problems, this is the dive computer to get; its the only one I know that vibrates.