I started with the Belkin N52, way before Razer got the licence to build them and I haven't gone back to the keyboard ever since.
Friend could not get used to it, but I found it perfect. I have now retired the n52, but because the D pad to the side wasn't responsive anymore; the joints dissolved from all the usage. It still "works", but you have to almost hit the Dpad buttons for them to react.
All in all, getting a Tartarus or an Orbweaver (which is the one I have now) is a great experience changer. If you haven't tried one out, I really really tell everyone to at least give it a shot. You might just never go back to a keyboard (to play games, that is) anymore.
I have the Logitech game controller which is similar. Use the thumbpad to control character movement in most games with a WASD also set in the keys. Use mouse to aim & fire as normal. Works quite well for me. Will try a Orbweaver when/if the Logitech craps out.
Used the G13 for a bit but for the first time in my life I'm using WASD now, mainly as its more convenient for when I want to type in game. Also the joystick on these things aren't nearly as compatible as you would hope, nothing is as universally compatible as WASD