Received mine today. Here's a size comparison of the Rival 100, Zowie FK, and Razer Deathadder 2014.
It has a downloadable configuration tool called Engine (screenshot), similar to Razer Synapse, however it does not require you to make an account. The LEDs can be changed to just about any color you want, other effect option are Breathe (slowly fade in and out) and ColorShift, which scrolls through one of four preset color palettes.
Engine includes a program called GameSense (screenshot), which allows you to change the LED based on certain conditions like low health or kills and whatnot. Downside is, it's currently only active for CS:GO, DOTA, and Minecraft.
ViperAlways wondered about SteelSeries mice, looks like this one is a really quality one to tryout.
Also, it says the mouse tops out at 4000 dpi. over 8 steps. Anyone know the increments then? My guess would be 500, 1000, 1500, etc.
250, 500, 1000, 1250, 1500, 1750, 2000, 4000
Neat customization features aside, this thing has a fat ass. The Deathadder is ergonomic, but it's hourglass shaped. This one feels like they wanted to do something similar, but gave up halfway. I'm kind of disappointed that although they have a nice configuration tool, they don't have a whole lot of options for DPI below 1000, plus coming from the Zowie with 1150 DPI it's kind of awkward having to jump +/- 100 dpi, but that's just a personal thing.
TL;DR: Mouse has good customization options, is pretty cheap ($35.99 + free QcK mousepad), got booty, but awkward sensitivity stages.