Overall, the success rate of the Tippr deals I have bought have a 50/50 chance of being usable. Even when it is successful, they are slow to ship products without good customer services for reassurance. Additionally, vouchers are not stored properly into my account so I couldn't even print the voucher for when I used my service!
There are some questionable businesses that they lure into their services - my friend bough me a voucher for an airplane ride and the information was incorrect and my friend never got their money back for services not rendered.
Never have had problems with Groupon and LivingSocial. You are better off with one of those deals