I have this mouse and I really like it. I haven't played more competitive fps like CS in a while, but I've been playing l4d2 and it works well.
The battery life really isn't an issue for me. There are 2 things you can do:
1. Change/set up a profile for general computing use. When you're surfing the web, watching vids, typing articles, doing hw, etc you don't need the higher poll rates. I keep my poll rate at 333 for normal use, and I have different profiles when I'm gaming. So basically if you only use higher poll rates for gaming, then you can expand your battery life for a lot longer.
2. Buy some rechargeable batteries. I bought a charger that came with 4 powerex 2700 mah batteries and it's great. Whenever the batteries die or are really low, I simply swap it out for a new one. It takes 10-15 secs so if you're worried about your mouse dying while gaming, you can swap it out during the end of a round or when you're respawning.
I can use 1 battery for days and usually I can use one for a whole week. With the 4 I bought and the one that came with the mouse, I have 5 batteries total. I basically only need to charge my batteries once a month and since I have a battery recharger for that, it's even simpler because I charge 4 at once.