Just me 2-cents for the next to nothing its worth: I've been using Mandriva for quite some time (since 6.5), and for all the fun that 'real' Linux users make of it, I think that it has become wonderful. When I got the 2005LE, I found that as long as one has some basic Linux knowledge, it was easier for me to install than XP, and I can do that in my sleep. Then they goofed (by releasing the atrocious Mandriva 2006), but made up for it (at least to me) with their wonderful 2007 releases.
While not the purist view, I am all for and completely enjoy the refined KDE interface Mandriva comes with. Once one spends a bit of time getting things where you want them (just like in any other distro), its different than Windows but every bit as functional; there are things that I cannot do in Linux (due to lack of software) but there are many things that it does much better in my experience. I also find it to be faster than Windows XP doing most things, but it should be; it’s a 4-year more recent OS.
I’m currently using the 64-bit version of the Mandriva 2007.1 and although I read much about issues with 64-bit Linux, I am not having any at all. I play all of my DirectX games in Windows and all of my OpenGL games in Linux; the latter includes UT GOTY, UT2004, Doom 3, Quake 4, Wolfenstein ET, Tremulous (whacked!), Serious Sam TSE and a few others, all of which play great. I even run my X-Fire in Crossover (Wine), but cannot chat in game

.
The only serious issue that I have with it is that if one enables the awesome 3D OpenGL desktop it has a serious effect on OpenGL games…like they won’t work. Other than that, I am completely satisfied.
So, though there are other distros that I really like (Kubuntu mostly) I just see no reason to look into a change. I’m sure that the folks that are satisfied with other distros feel much the same; it works, so why fix it?
Good luck with your distro-hunt!