Everyone has an opinion, so I will add mine! Here are the pads I have used, in order:
Everglide Giganta: Basically a hunk of underengineered plastic. It felt awesome the first two weeks, pretty good through the second month, but after that the middle of the pad became too worn for comfortable usage. I went through two before realizing that they were a money dump. Consistency and longevity are important! At the time, Everglide.com also charged as much for shipping as the pad itself. This was about 3 years ago and I am not sure if they have corrected any of these issues.
fUnc 1030: I bought this pad before reading many reviews on it. My first impression was that it was $20 well spent, due to the packaging, accessories, and two sided surface. It felt like a well-polished product even though I bought it shortly after its introduction. Both sides are slicker than a standard cloth pad or wood surface, however I adjusted quickly and the textured side (the faster of the two) is now my preference. In my experience, this pad is good for about a year under fairly heavy usage.
Icemat: While using the fUnc, I thought I might try something new. I don't recall the exact figure, but this pad cost at least $30. Unfortunately, this was not money well spent. The glass surface was what caught my attention since at the time I had been looking for a replacement pad that would never wear out. I ended up only using this pad for a few days. The glass surface was prone to collecting moisture (yeah, wrist sweat!) which would significantly slow down mouse movement in those areas of the surface. Windex remedied the problem, but having to clean the pad daily was annoying. The speed of the surface, in a clean state, is between the speeds of the two fUnc surfaces.
Ngen C4 son of something (beta): This was an interesting pad to test, and free was a good price. The teflon surface certainly had merit, but like the Icemat it would collect gunk and require daily cleaning to maintain its consistency. I also perfer a pad that sits up off my desk a bit, probably due to conditioning my wrist on such pads for the past few years. The next revision of this pad may be something to look out for.
The pad that I still use and would recommend for a gamer is the fUnc 1030. It is the most consistent, longest lasting, and lowest maintenance pad I have tried. I would also suggest investing in some teflon mouse tape to cover your mouse feet. These help to reduce wear on the original mouse feet. When the teflon tape wears down (usually after 2-3 months) it can be easily replaced to maintain a consistent level of smoothness.