I've got my eye on the G403. Wired for $35, Wireless for $40. Both seem pretty close to historical lows. Tried it out in store a week or so ago and was happy to find out that it felt comfortable to use and reasonably close to the MX518 that I've been on for ~10 years.
I have the G403 Prodigy (USB Wired). I love it. While I do wish it had more buttons on the side and/or on the top left (i.e. see the 502 Proteus' design; I really want *that* mouse) - it's easily the best 5-6 button mouse that I've ever used. Certainly beats my Rosewill Jet Gaming Mouse. Not even close.
It comes w/ a small 10g weight - so if you need the mouse to have more weight to it, you can throw that weight in there on the very bottom of the mouse. There's a little slot, where the weight can go. Or, if you like it lighter (which is how I like my mouse), just don't put the weight in there.
I also love the Logitech Gaming Software that you can use with it (you have to fetch that online) - you can set-up templates for games, use them for other games (good for if you want one FPS to play like another), create actual profiles for each game, or whatever you desire.
In Logitech, I trust.
I have the G600 MMO. It's bulky and has a real learning curve to get used to - since it's bigger than most mice and also has tons of keys on the left side of it. But, I only now really use that if I have a game where I really feel like I need to stick tons of keys on the left side of the mouse.
I really want that G502 Proteus (with 11 buttons all over the mouse), which looks like it could be a possible nice go-between for the G403 (around 5-6 buttons) and G600 (i.e. 12 buttons or so on the left and a few more elsewhere)