Not much for keyboards but...I have a microsoft intellimouse explorer and it is awesome.
It is the only five button mouse that is still compact and comfortable for me. That aside, you can assign mouse4 and mouse5 to be linked to ANY KEY ON YOUR KEYBOARD, so there's none of that "oh I have a five button mouse but my games don't recognize them" crap. Mine are bound to the comma and the period, respectively, and the buttons work in literally every game I've ever played. Also it is a laser mouse but the eye is very sensitive and I never get that annoying "oh you moved the laser mouse to fast so the cursor read all wrong" problem. It is silky smooth and I've had one for years...when my old one broke I went out and bought a new one immediately. I only paid about 50-70 bucks for it american.
Believe me, being able to reload on the mouse button, or dive with the mouse button is worth it, man. I even set up my smaller side button (mouse4, aka comma) to select melee in esf...so even if I'm shooting a beam I can quickly jump back to melee in time to defend an incoming attacker. And if not my other mouse key is block.
The only thing I notice is a very slight delay on one of the buttons but that is rare and it may be isolated to certain games or my system. Setting it to reload in games like Battlefield 2 is very helpful; it never locked on me or failed to work either, there are just moments when it had a slight (less than half a second) delay, so I wouldn't set it for something like say jumping, but reloading or using things or setting it to mouselook is really great.
Man you should have seen me during the tribes 2 days. Shooting, healing, reporting the enemy position, throwing grenades and laying mines all at the same time with one hand...insane.
I love my mouse. :0)