I actually wanted to bring this up before, but was told in chat that it was an odd topic as everyone has their preferences...so i avoided it.
So...it all depends on what you do; I assume gamming. I do more than games, so I'll drop my 2-cents on both aspects (work and play). First, let me point out that the bluetooth-type MX's MAY have a lag that no pad can cure. I've just heard of a few members having response issues that I don't have with the standard mx700/1000.
For General use, I simply use a large piece of craft foam. I'm not sure what it should be called, but I found it in my daughter's closet and started using it on my keyboard tray. Of all the colors, I stuck with a light grey. Mainly for the same reasons One4 already pointed out, but I get white too dirty, too quick. I use this simply because it's large and comfy. If I just used the wood tray, I'd scratch it all up and I can replace this foam stuff cheaply (just go raid the closet monthly:p) I've tried spraying pledge on it for games, but it soaks it up within 30 minutes and it needs another shot. After a week or so of this, it gets nasty so I use a real pad for games.
Oh ya, games! I use a RatpadzGS, but it's some off-edition from FrozenCPU for a couple bucks more. I have no idea if it's better than the standard GS and I see nothing visual to tell them apart besides the frozenCPU label. With the MX700 (and basically all the logitech opticals I've had), the little feet fall off. Another mystery, but with my faithful 700, the rear pad wore thin and one on the right fell off. So, I bought some teflon mice feet over at FrozenCPU to cover the spots. It comes in a strip and you just cut little pieces off...and it's slick as shit on the Ratpadz BTW. I also tried using pledge on the Ratpadz, and it's just too damned slick for my tastes in FPS's. I adjust the sensitivity in-game, so maybe if it was at the default level, the pledge would be perfect. Oh, and if it matters, I have a polygraphix (it has a different spelling, I'm sure) cover for it. It just adds a graphix to the boring black surface.
I also recently just got the mx1000 and have yet to see any real difference with being better with one pad or another. But I do see that this one likes black shiny desk surfaces where the opticals would not respond.
I've tried the C4 cover prior to the polyGFX (or whatever) and didn't see what the fuss was about. It was slick, but again...maybe "slick" isn't for me.
And I've stuck with the Ratpadz unit basically because everything else was loud and the "clack-clack-clack" got old at 2am...and not just me:p