Luth wrote:I have
this for the left hand and
that for the right hand.
The gamepad + mouse are about 5 years old now and i don't have any problems with them. I just had to fix the doubleklick problem on both mousebuttons once, but this occurs on every mouse after some years (it took about 2h and a shitload of patience

).
Both are a little expensive (especially the mouse...), but it's not so much money if you calculate it over the whole time.
Counterpoints:
Gamepad: the keys are a little hard to press
Mouse: the keys 10-12 at the keypad on the side of the mouse are hard to reach, if you don't have hands like an elf
I never turn with the keys, the sidekeys are bound to the strafe directions. I always walk with the keys and turn with the mouse (left for camera turning and right for character turning; no mousewalking).
I use the keyboard only for typing in the chatwindow or hitting escape.
Funny comics about this topic:
http://www.darklegacycomics.com/87
http://www.darklegacycomics.com/107
It's WoW, so beware!

While I 100% recommend using a gaming mouse for MMOs, I URGE you, to stay as far away as you can from Razer products. ESPECIALLY their mouses (mice?).
I bought a Razer Naga, the one mentioned above, and after only a few months, the buttons stopped working. I had to literally SMASH the buttons for it to respond. It got worse and worse, day by day. All the way uptil I finally had enough and went out and bought a new mouse.
But I though to myself: "That's a shame. I was probably unlucky. I'll give Razer another shot!". So I bought ANOTHER Razer Naga. And guess what? EXACT SAME F***ING PROBLEM AFTER A FEW MONTHS! Buttons just stopped working.
And to make matters worse, I had a friend who bought a Razer Naga, too. He bough his like a week before I bought my first one. And you'll never guess what happened to his. I'm not even kidding. It had the same flaw... He didn't give Razer another chance. He went and bought a Logitech mouse instead. I honestly felt like a fool for giving Razer another chance.