i use Mecanique EasyHID. Not much.

It do everything you need to start.

http://www.mecanique.co.uk/products/usb/easyhid.html

Well, if it's not enough, you could still break the bank and waste that 600USD. But honnestly, i don't see ANY advantages... unless you don't want to scratch your head a little bit.

Follow the USBDemo and Darrel's instant interrupt thread. Should be something to read and try first.

It's still your money so far