Well I thought it was time for a new mouse. Well in truth I buggered my old IntelliMouse Explorer 1.1 up, by trying to get some dirt out of the lens with a screw driver (it was all I had to hand at the time) which crippled it, it become very picky over what surfaces it worked well on (the top-right corner of my mouse pad basically). Note to self, don't jam screw drivers or hard objects onto the lens of optical mice.
I picked up a IntelliMouse Explorer 4.0A (wired) for £15 which was a great price.
Wow what an improvement, it's really come along way from the early models. The tilt wheel is a bit strange (but I guess we said that when Microsoft added the scroll wheel to mice). The middle mouse button is much harder to use with the tilting wheel, this is partially due to how I hold the mouse, it needs to be clicked sort of backwards towards the mouse, I tend to hold the mouse with my hand much further back, making the angle a bit harder to reach (it's still usable it just needs a bit of force). I've redefined the middle mouse to one of the side buttons - I never used them anyway on any mouse. Build quality is great, very solid feeling mouse. After upping the PS/2 sample rate to 200hz it's so smooth. Not to mention it's very smooth when moving over my mouse pad, it really seems to hover above it some how.
Fantastic mouse and if you can pick one up for £15 do it.