I come from a Windows background, and still use it at work every day. My work laptop is Windows XP SP3 and it works well enough. Being a work laptop, I do not do my testing on it, I have other machines for that.
My parents have their own computers that I maintain. I have finally got them to stop hitting every "scan you computer now, you have a virus" window that pops up. My dad's computer is a Dell Inspiron from 2007 with Vista 64-bit. It works, and I have yet to have to do anything but clean up some temp files (normal for ANY computer) and apply patches - I have it set to notify and I have him call me when there are 10 updates. My mom's PC is an HP Voodoo (my old one) with Windows 7 64-bit and I rebuilt it before I gave it to her. Same process with that one as well. They have a shared HP 27" touchscreen desktop that is set up to do the updates on its own - they use it for storage and my mom does her photos and business documents and books on it for their real estate properties. On all of them I have AVG Free and Windows Defender running. So far, I have had to deal with 3 viruses since 2007 on their machines. The key piece to all of this is LogMeIn.com is on every one of them. I rarely have to go over and do anything.
On my own MBP, I still have Windows 7 installed in Bootcamp. It will be there until I have no need for it. That is coming, I am getting latest Final Cut Pro for myself for Christmas to replace Sony Vegas. My last app to replace is Photoshop CS3. That one will be hard to replace. I lost the (they were stolen from my bag at a coffee house) original install disks and cannot get the switched license without them (spent 2 hours on the phone with Adobe about it.) However, I have found that I have not been using much more than Aperture in the last few months anyway, so it may be time to reclaim my drive space...
When it comes to Windows (XP, Vista, 7) it all depends on how you use it. It will let you do, literally, anything. It is a nice draw. You can change the look/feel so much easier, and really, especially Windows 7, is an easy (comparatively speaking towards the older Windows versions) OS to learn and use.
Will I never buy a Windows machine again? No, not never, just not soon.
Will I only ever buy Apple machines from now on? For myself personally, probably.
Will I recommend Apple over Microsoft to others? Depends on the person.
All computers, regardless of chassis or OS, run on the GIGO (Garbage In, Garbage Out) principle. They do nothing more than what we tell them to do.