Suppose I could be riding the wave here, but with all the iPhone talk I figured I'd chime in with the "okay, what ya been doing?" answer... At my new job I now work on a Mac book pro. Yup, as far as Bill Gates is concerned I've gone to the dark side. Of course, there are a few tools that I would recommend when you land your new Mac - especially if you are coming off of Windows.
Adium is Trillian for OS X - a one stop IM application that can aggregate all your IM contacts into one place. I have friends on AIM, ICQ and MSN. No problem. Adium had a few IM protocols I had to go look up!
I had been using Launchy on Windows, which was inspired by QS. Both applications search, and index information and applications on your HD. You can then launch QS, key in a few letters, and bring up anything from your favorite website to an application. QS wins where you can now take it a few steps further. You can chain QS commands into actions. So I can say, take this file, and move it to, this directory. And it's done. No Finder, no drag and drop, just keyboard.
On Windows I had been using jEdit and Notepad++ for text editing. While the built in Apple text editor was okay, I missed having tabs for editing (I'm not a multiple-window guy) multiple files. TextWrangler filled that gap and does very nicely. I haven't tried it for code, I still fall back to VIM - don't bother selling me on Emacs, it wont work.
There are a few more that I'm playing with to get things settled, but nothing worth mentioning till I get more into them. And yes, if you ask me about the Mac, "It just works." If you haven't tried it, you wont believe me. I can see why the catch phrase is so overused.