Had an old boomslang from way back in the day, when they kept the ball for weight. Was a great mouse, comfortable to use and great in-game, but it broke after about a year and by that time Razer had gone under (years ago).
So then I got a Razer Pro 1.6 about a year ago (white version of adder, basically. Drivers were a little awkward but useful, and the mouse felt a little light and plasticy, but overall it was a definite boon to my gaming. After about 6 months or so it started acting up, randomly disconnecting and even BSODing a few times. At the time Razer only offered support for products ordered from their only store unless it was bought in Canada, and insisted I return it to the vendor, which I couldn't do because it was a GCO order on Buy.com. Just recently though, they started up a support site, but dealing with their support staff is a pain to say the least, with most calls being me just saying 'check' as they went through their lists whilst I really just played solitaire...
Contrastively, my gf's MS optical 4000's scroll started feeling a little sticky at one point, so with just my name, address, purchase info, and a scan of the bottom of the mouse faxed to MS supplemental parts, I just got a replacement sent to me in less than a week. Meanwhile, I'm waiting on my RMA from Razer, playing instead on my 10yr old MS optical basic.
Also, 4000dpi might sound like heaven, but keep in mind you'll never use more than 400-600dpi unless you want to spin in a full circle by moving the mouse a quarter inch. Real strong suit I feel is in Photoshop, where I can use the toggle keys to dial up and down the sensitivity, wherein TF2 I just have sensitivity and acceleration setup in each class script.
Sorry for the thread-crapping, but I guess the moral is don't get yourself caught up in buying specialty gaming hardware, and instead rely on the tried and trues like MS and Logitech.