I am an avid baker and over the years have been using silicone mats to bake my cookies on. I recently switch to Silplat mats after seeing them being used on all the cooking shows. They are fantastic. The old silicone mats I was using works really well but they were slippery and sometime difficult to use. The silplat ones grip to your pan and stay put. They help cookies to brown evenly and then when they are done, they slide right off. I always get asked how my cookies stay golden brown on the bottom and do not burn. I have also used mine to roll out fondant and dough on. The grip keeps it stuck to the counter when you are rolling so it does not slide and I use less flour because of the nonstick surface and that results in more tender cookies and doughs. The one thing you can not do on the silplat though it to use knives and cut on it because it will mess it up.
Update On Mar 11, 2010: I have been using this Silpat mat for over 2 years now and it is still in perfect condition. I now not only use it to bake cookies on but I also use it to roll out dough and fondant on. It makes a great nonstick surface and is also much easier to clean than my countertops.
I have purchased a few new matts including one of the larger ones which is the one I use primarily for rolling dough. They may be a little expensive to purchase at first but they work great and last a very long time so you really do get your money's worth out of them.