I bought this Mac (my first) knowing that I would never stop using Windows - it is necessary for the work I do, and there are Windows applications I have for personal use where there's no Mac equivalent (even though in a couple of cases there are Mac versions). I've recently become serious about learning digital photography, and I'm using the OS X solely for photo processing applications and related software. So far, I would say I'm in Windows about 75% of the time (alone or alongside Mac applications). I've discovered that there are a few things I like better in Windows (like Windows Explorer versus Finder, though I love the search box in Finder, etc). The downside is that I'm still spending a lot of time doing preventative maintenance in Windows (it is still after all, even on a Mac, "Windows"). The Mac side has been trouble free, which is what I was expecting. And three to four years from now when I'm ready to replace this machine with my second MacBook, migrating to the new one will be so much easier than what I've experienced with Windows.
I know that there are plenty of Mac and Windows zealots out there - fortunately I'm neither. I'm just very pleased to have one machine that provides the best of both worlds, for what I need and want it to do.