been some time since I bought that mouse due to the feeling that I need a symetric mouse for gaming and indeed, it gave me a new feel to the game.
What it didn't give me is the simple Input I need from any gaming mouse, more about that later.

First on, no info I write here is validated, however you guys know that I am trying my best to get everything out of a mouse I own.

First trys month ago after informing myself about what is inside the mouse, I expect it to be a special version of the sensei with some fancy printing on it, sure why not: unboxed it, plugged it in, started the steelseries engine and did some basic configuration to play with it. The big and stiff mouse cable seems to be very durable, but doesn't do any benefit to gaming. If steelseries really would like to do something good to their gamers they would invent a swapable cable. - In first week it turned out 400cpi doesn't do the trick to get a similar sensitivity, 500cpi was rather similar to what I used in past, so far so good.

been gaming with it now for 2 months and my feeling about it is playable, but not top notch.

Mouse buttons: The buttons are nothing special, it clicks like any other mouse, buttons have zero problems with gaming.
My statistics according to the steelseries engine:
Mouse1:376529
Mouse2:116734
left side button:15408

Remember, I trashed my deathadder because the plastic of the left side button broke and even if we triple that value this tells us razer is just cheap quality, as known already 5 years ago. (however no sensor ever came near to the deathadder sensor besides the fact it had some skipping on bad surface).

However seeing that I use the left mouse button 3 times as often as the right one, a lifetime of 10 million clicks doesn't seem much special, especially since I know how to fix omrons and my other mice have a lot of clicks on them without any stupid "MAX LIFETIME" marketing. So ofc never trust companys

About the shape, it is similar to the wmo, but basically worse. Why? Because the large end of the mouse enforce you to keep your fingers on high of the sidebuttons even if you don't need them. Or with other words, you can't grab the mouse as good as most other random mice if you have average hand size. As bigger as worse. Anyways playable.

So I had some test and run comparisons with the other mice I had at hand right now (unfortunately, no deathadder, otherwise I would have used it as comparison.)

So I did the common 360 test based on dpi and 2 driver versions, it performs really bad compared to the other mice.
wmo:29cm
3.0:29cm
MX318:29cm
steelseries:28cm@500cpi,35cm@400cpi
1000cpi with half sens compared to 500, 28cm.

furthermore on high speeds it does a positive acceleration with makes any flicking around impossible, same reason I got playing with cl_mouseaccel.
My Theorie, Steelseries renders the input down to 80% for the first 2m/s just to go faster, the max is somewhere about 3m/s because I could make it skip on really fast moves. The mx318 (if you don't know, it uses same sensor as the mx300/mx500/g1 but only at 6000frames instead of 9000) performs way better in terms of sensor. 5700 cpi are also marketing, noone ever needs that. However I was positive surprised that it seems to take any surface without a problem.

Final conclusion:
The symetric form of the mouse really performs better compared to asymetric, however the positive acceleration kinda makes everything this mouse has bad.
So I am reverting to ie3.0 for the moment, if I buy any next mouse it will be the ie1.1a. WMO is a good mouse, but the buttons are to cheap and it has no sidebutton I need for sniper zoom in other games. (in Q3 I zoom like one time a day max).
so far from my side steelseries isn't the way to go, however remember you always need to make urself an own opinion.

ps: googling about the positive accel brought this quote:

I don't belive anything on the net but such words don't come from nowhere.

pps: if somebody needs a good guide about keyboards, check out this:
http://www.overclock.net/t/491752/mechanical-keyboard-guide