I have to disagree as my experience with Vista was buggy, slow, unresponsive, and just a drain on my resources.
Windows 7 has been nothing short of a very pleasant experience. I think Windows 7 is a great step forward and M$ finally found its replacement for XP.
Now, since using 10.5.6 OS X (Leopard) on my Dell Mini 9, I have been really liking it. I was not familiar with OS X beforehand, too much, so I have yet to become completely accustomed to the OS as of right now. I feel like once I learn a bunch of keyboard shortcuts then I will enjoy the platform even more.
Sometimes my Mini chugs along for certain tasks but, overall, I just enjoy playing around on my Mini ever since I got it. I purchased it as more of a toy and something to hack so it has been worth every penny to play with. I'm glad I purchased it.