There are a number of good programs for the Mac that do TABS. I have used Macs exclusively since 1986, and I'm in the same boat as you guys.
Here's what I've found. THey're all pretty good, some better than others obviously. But if all you want to do is write out TABS, these will do the trick. Some are free, some aren't.
Guitar Pro - $60.00
Transcribe - $50.00
Tux Guitar - Free
Tux Guitar is very powerful software and does more than just transcribe songs. It works great and is updated frequently. It's also easy to learn to use.