Purchase!
It really is a great tool. If you spend enough time to tweak it, it can become absolutely amazing and perfectly intuitive. I'm very frustrated when I need to use a trackpad that doesn't have side-track features. (I also get frustrated when settings aren't the same as mine, but thats minor)
You won't find a tool with a better usefulness to price ratio. It is a small price to pay for something that you use 90% of the time you use your computer.