I've mining with rented rigs at mintsy for a day and it sucks. I wouldn't even call this an alpha site much less a beta test.
Give us some feedback on what you dont like about it? Being an early invite Beta there are definitley going to be issues to sort out, but without feedback hard to identify them all at the same time?
The mining contracts are priced ridicuously high at about 3 times what it will ever earn. Buying a mintsy mining contract should be considered buying a lottery ticket on the future price of BTC.
The issue with BTC mining in general right now is its not cost effective. So when the difficulty is high and the price is low the contracts can appear to be to high. On that note if the price goes up and the difficulty drops... It can be a bargain. Do you have a cheaper place you can buy Scrypt and Sha contracts? I'd like to know? I'd also like to point out is they will be trade-able which in a sense will help on the ROI.