I’ve had a Diamondback for about a week and a half now. It’s a really nice mouse, despite the drivers (see below).
It’s lighter than a Logitech MX310, but heavier than an MS Intellieye Optical (the symmetrical one). The shape reminds me of the old Logitech Pilotmouse+ (which is a good thing). It’s slightly steeper at the back, but not like the MX310 (which is more of a wedge shape, and not very comfortable).
The buttons are slightly misleading, I think - there are seven, including the wheel (or nine, if you include wheelup/down, which you shouldn’t). However, they’re really only usable with your thumb, as the ones on the other side are too small and badly positioned. Realistically, this gives you five buttons. I’m fine with this - I only need five, and I prefer having two thumb buttons to one thumb and one finger, which is what I had on the Logitech MX310 I was previously using. Your mileage may vary. No buttons either side of the wheel, btw.
So, the drivers then. Here’s a small blow-by-blow account of my attempts to get it working:
Wednesday:
Get mouse.
Try to install mouse. During install, a big ‘FAILED’ button appears when detecting mouse. Frown a bit, but notice that it hasn’t halted the install, so carry on.
Open the Razer control panel applet and try to set up sensitivity. Note that none of the settings seem to have any effect.
Try Windows XP’s mouse control panel applet and successfully turn sensitivity down and acceleration off.
Root around the device manager and discover that Windows XP hasn’t detected the mouse (hence the ‘FAILED’ above), and is using some standard HID mouse driver for it. Consequently, the control panel applet that was installed with the Diamondback drivers is doing bugger all.
Finish work, take mouse home, try to install it on home PC. Same results as above.
Browse the tech support section of Razer’s site and find nothing useful.
Go to bed, muttering.
Thursday:
Machine at work refuses to boot up - the windows install is corrupt. Frown a lot and stare accusingly at Diamondback. Decide not to try to use Diamondback at work again until driver crapness is resolved.
Get home, root around the internet, find a .inf fix for the Diamondback which allegedly fixes the ‘FAILED’ business.
Install .inf fixer, apply it to latest official drivers on Razer’s site and follow instructions on how to update the device in the device manager.
Razer control panel applet now works… sort of. Can adjust sensitivity and turn off on-the-fly sensitivity and acceleration, etc., but can’t reassign side buttons properly.
Browse the tech support section of Razer’s site again, and find an article on fixing the buttons.
Reinstall everything (including .inf fixer) after cleaning out old/temp driver directories etc, to no avail.
Send mail to Razer tech support with details of problem.
Friday:
Get home from work and check mail to find automated reply from Razer tech support saying someone will respond to query within 24 hours.
Spend rest of evening using mouse with no side buttons.
Saturday:
No response from Razer. Not expecting one over the weeked, anyway.
Sunday:
As above.
Monday:
Check mail at lunchtime.
Check mail in the evening and find one from Razer tech support. This time it’s only slightly automated and asks me to send an msinfo.txt to them with details of my problem.
Generate msinfo.txt using instructions in email, and repeat details of problem again via ctrl c and ctrl v.
Recieve another automated email from Razer a few minutes later stating that someone will email me in 24 hours.
Tuesday:
No response from Razer
Wednesday:
As above
Thursday:
Email from a Paul S at Razer, saying they’re looking into the problem. He suggests I try the beta drivers available on a third party site, while going to some length to explain that they aren’t supported by Razer.
Mutter to self.
Try beta drivers on top of existing ones. Install seems to go ok.
Razer control panale applet won’t start, complaining about not having the right files in certain directories. I find them and move them there.
Try control panel applet again. Everything seems to work, including side buttons.
Decide to take mouse back into work and try there tomorrow.
Friday:
Take mouse into work and install beta drivers from scratch. Discover that the device hasn’t been recognised again.
Uninstall everything, and reinstall the latest official drivers from Razer’s site. Device isn’t recognised again (no surprise there).
Apply .inf fixer, and update drivers. Mouse is now recognised, but no side buttons (as expected).
Apply beta drivers over the top of official ones, and everything works again, except the control panel applet, which has no effect on any of the settings (although they all work as I set them up initially).
Uninstall everything and delete temp files, rebooting each time. Reinstall everything as above, and find it all works this time, including the control panel applet.
If you can be arsed jumping through hoops like that for a while, you’ll probably like the mouse. If you don’t particularly want the side buttons for anything, it removes one of the hoops 
I’m sure Razer will sort the drivers soon, in any case. If you’re left-handed I think it’s worth perservering with, because it’s much better than either of Logitech or Microsoft’s latest symmetrical mice. If you’re right-handed, you might be better off with a Logitech mouse.