110% cashback is a signal for me that it is shady. Well OP I suggest that you should not join the site and this is the first time I saw a website that gives its user a 110% cashback. It's better safe than be sorry at all.
It's 110% on the commission paid, so if it's 3% cashback you'll get 3.3% instead. And since their payout percentage is less than other cashback sites that's where the miracle extra payment is. For example they pay 8.8% on Avis. Topcashback.co.uk pays 12%. Cashback usually takes so long to pay out that this might still be a better option if you think the price will rise in a few weeks or months.
Cashback for BTC is definitely an appealing idea but cashback via the established sites is often sketchy enough. I've no idea how good or bad this would be. It might be worth a test at least. It's not as if you're risking a great deal.
