Macs seem to be insanely popular amongst CS faculty. Most conferences and faculty meetings I go to are dominated by Mac users. No big surprises, since (a) Macs work, and (b) they're sexy. I switched from Linux to Mac a couple of years ago after I got tired of editing three configuration files and rebooting to join a wireless LAN. That worked when I was a grad student, but now I'm too busy for that kind of crap.
I wanted to share some links to good Mac specific tools that I've found to be very useful in my job. If you have other suggestions, please share them as comments!
OmniGraffle is a great figure drawing program and produces very professional results. It's also easy as hell since it can do most of the layout for you, making sure that the boxes and arrows all line up correctly. The PDF output looks very slick and I've been using it for most of the figures in my papers; see Figure 1 in our SenSys'08 paper on Pixie for an example. Be sure to get the educational pricing.
Papers is one of my favorite Mac apps. It's like iPhoto for PDF files -- it will keep track of all of your papers, index them by title, author, keyword, etc. I use this program to keep track of my ever-growing reading list (rather than printing out a bunch of papers and letting them collect dust on my desk.) It also has a pretty slick interface for matching metadata about a paper (e.g., to pull in full citation information from the ACM Digital Library or Google Scholar) and for exporting to BibTeX and other formats. You can take notes and there's even an iPhone app (and soon, an iPad app) to let you read and take notes on papers on the go. (Yes, reading a two-column paper on the iPhone screen works -- if you zoom in on a single column and go widescreen, the text is the same size as on a printed page.) The only downside is that you have to manually synchronize the Papers library across multiple machines, easily accomplished with Unison, but I wish that were simpler.
BibDesk is a BibTeX library organizer. To import a new BibTeX entry, just copy it to your clipboard and paste it in BibTeX -- everything appears in the correct fields. You can also drag and drop BibTeX entries between files. This is infinitely easier than editing BibTeX files by hand and keeps the formatting right.
OmmWriter is a fantastic little app that is a essentially a Zen text editor -- it clears your entire screen and shows you only the text that you are writing. This is a great way of minimizing distractions and focusing while you write. WriteRoom is similar but I find OmmWriter's interface more appealing.
Finally, Caffeine is a little app I could not do without -- it puts an icon in your menu bar that, when clicked, disables your screensaver. This is very important when giving talks and avoids the embarrassing moment when your screen saver kicks in mid-presentation.