I have got a pack of 10 free proxies as a review copy. They have been test for last 3 days. Delivery, response time and support is great. It was quick. I would give 9/10 for that.
When talking on performance and speed of the proxies, I am pretty satisfied when compared to other semi-dedicated proxy subscription I use. There were NO downtimes. But it would be nice if OP can increase the speed a little bit. As a new service, it is good.
So overall I would rate it 8/10 considering all the aspects. I would like to give some suggestions as well to improve the quality of the service. One is the implementation of IP authentication. That would improve the performance much more. Also if OP can start giving away dedicated proxies, for a higher price, that would bring much more customers. I prefer dedicated ones over semi ones especially for SB since they perform much better.