There are plenty of in depth reviews out there that will cover the differences probably far better than I - and take less of my time
However I can simply say that I have no regrets as the build quality feel and innovation/implementation is superb. As to whether its enough to justify the huge price tag, that's really subjective personal opinion/perspective. Alongside say that of buying a mega expensive mouse.
In short: no regrets and no I wont be sending it back. Its my precious.
Ok cheers, yeah I know an in depth review would better but sometimes a first hand experience account from someone is better

The price is really steep for one, maybe next year I will see if they come down a little or find a valid reason to get one
