Thanks for replies and sorry for delay! (had to fly out for work at short notice).
The mouse in question (not the tiny, crappy, laggy thing i'm using on my lappy right now) is a microsoft wireless 2.0. I don't know if it's the "ergonomic" model or not, but it's shaped like a futuristic sports car, quite big and probably designed with gaming in mind. It came in a package with a wireless keyboard (which i abandoned long ago) and was given to me as a present at a time when i was both anti-optical and anti-wireless and it completely converted me way back then. Based on the assumption that wireless can only get better, i don't think i'll ever be reverting. As with B, whatever lag it has is not noticeable by me, and i do use mine for 1st person shooters and stuff. If i have lag online, then it's certainly not the mouse's fault.
The reason i need a new one is only due to the wheel bearing finally giving up the goat and being something that can't really be cleaned, repaired or replaced. The rest of it is fine and i will definitely be keeping it as a spare.
Elfbane - extra cost associated with batteries isn't an issue. Long ago i got in the habit of keeping spare batteries for the mouse, so even short battery life isn't really an issue. As long as it gives me a day or so's notice before it refuses to work (as the old one did) i can live with it.
B - I got pissed off with logitech mainly due to the annoying software and compatability issues at the end of all the annoying software. I don't need 4 processes or more running for a mouse/keyboard combo and constant pop-ups reminding me to upgrade annoying software. I also don't need on screen reminders of the brand of peripheral i'm using. That's actually a deal breaker for most things for me. Epson is next on the shit list. Sound advice on the rest, especially the wheel clicky thing. It's gotta be an audible clunck and not super sensitive.
TL - The mouse came with a large satellite reciever for both USB (which i never used) and whatever the standard mouse and keyboard ports are called. I think the last time i purposefully had to move it for better reception was 2006
otherwise it just migrates around the desk top or floor as it pleases, collecting dust or worse. It said to keep it 8 inches away from metal, but i don't think that ever bothered it.
Cerebro (hey mate
) - As mentioned, i've never had an issue with the mouse's gaming performance that wasn't battery related. This one didn't just cut out and it didn't have noticeable lag, and this is quite an old product now. I used to be anti-wireless, but this one converted me. Extra scrolling buttons and whatnot might be good, but they'd have to be in the right spots. That;s not something i can really know until i've used it for a while.
Wellard - I think there's a pattern here and its pointing towards microsoft.
In the time it's taken me to write all this, i think i've answered all my own questions. If only i could remember the name of the actual package. It'd save a lot of hassle.
Edit - In the time it's taken me to write this, Felix pops in too, with a rare prop for M$ no less! I do recall saying that my old mouse was the best microsoft product i had, and i have no great love for MS in general. That was years and probably one whole computer ago. I probably need to upgrade that statement to "one of the best [s]microsoft[/s] products i have.