Netflix is the only thing I can compare it to and although GZFX is much smaller, that is the company that they will eventually have to compete with if they want to keep afloat.
I have had a Netflix membership for quite awhile now and I haven't had any of the problems that you mentioned.
The only problem I have had is that I received defective DVD's on 2 occasions and as soon as I e-mailed them, they sent a replacement without waiting for the defective one to be returned.
Right now I will keep both memberships going and if there comes a day when Gameznflix gets close to the response time as Netflix, I will cancel my Netflix membership.