A long time Windows user, I've been using my new Macbook Pro now for a couple of weeks. As far as my experience with it is concerned, I have some good news and bad news.
The bad news is that I'd don't think the Mac OS is particularly better than Windows 7. In fact, I'd say there are some small frustrations. For example, I'm not sure how you copy a complete path name and paste it into Finder (Apple's version of Windows Explorer). I also like the way Windows 7's taskbar collapses several windows of the same application into the same taskbar icon, freeing up space on the taskbar. I can see how, at one time, Apple's dock would have been revolutionary compared to older versions of Windows. However, these days I genuinely think Windows 7 is a good user experience.
Beyond the OS, Office is the application suite that I -- and I imagine every MBA student -- uses most often. For Word, Excel and Powerpoint, I think the Windows versions are still far superior. I have Office 2011 for Mac and Office 2010 for Windows (thanks to some significant Kellogg student discounts) and I find the Windows versions to be two generations ahead of the Apple version. The ribbon interface, for example, just does not seem to translate as well to the Apple user interface. Thankfully, Apple have considered people such as me, and I find Bootcamp to be pretty effective for running Windows on the Mac. In fact, half the time I'm using Windows. With a little help from a hack, I also escaped paying the full cost for a full version of Windows, instead using my Kellogg super-discounted "upgrade" version for my Bootcamp partition.
This leads to the good news - the Apple hardware is significantly superior to anything else that I've seen or used. In particular, the multi-touch keypad is an amazing experience for scrolling through screens. Multi-touch is the strongest differentiator for me. The keyboard is also pleasant to use, and makes you feel like you want to type. The power-lead magnetically sticks to the laptop. The screen is sensationally bright and vivid. The battery-life is longer, though I'm not sure how long.
In sum: a mixed experience. If you're not using the Office suite, such is the case with many software developers, I can completely understand why you would want to just use a Mac. For those of us who love the Office suite's advanced features, dual booting is a reasonable compromise.