Which device are you talking about? There is a light duty, medium duty, and heavy duty Static Stretcher. The heavy duty stretcher is also known as the Static Vac.
Based on your brief description, I would assume you are referring to the Static Vac. Yes I have used it, in fact I have been wearing it for just under 2 hours as I type this. But I have only used it for a little over a week. My initial impression is favorable. I have read that a lot of guys who are not circumcised can have trouble with these devices. The Static Vac and similar devices must be removed to urinate.
I have not had any difficulty with blisters thus far and I have used it to stretch out to just over my BPFSL (just over 8.5"). There are a number of threads on this forum regarding the Static Stretcher, so do a search. Just be sure that you are reading about the version of the Static Stretcher that you are interested in.