+1 for MacDive. I love it for my Cobalt! Not only is it very "mac-like", but the support is great. The developer, Nick, has been great at answering questions on the support website. I'm happy to have paid for MacDive.
Also, with respect to the Uwatec computers... When using a Mac, you have to use the official (i.e. dive shop expensive!) Uwatec IR dongle for it to work natively with the Mac. I spent weeks trying to figure this out with my Uwatec SmartCOM. I thought "If my Mac Book has IR built in, why can't I use it with my SmartCOM?"
It's because the built-in IR is only on way: receiving. It's designed specifically for the little remote that controls iTunes and Front Row.
For a bit of sad irony, it turns out that you can use almost any manufacturers IR transmitter (i.e. Radio Shack cheap!) when running Windows XP in a virtual machine on a Mac. It turns out that it has something to do with the way the OS works with each specific IR chipset. Microsoft has an abstracted IR-architecture (hence the multi-vendor support), where as OS X requires a specific, low-level interface for each chipset.
I could be wrong, but at least that's what I've been able to surmise.
Kevin