We used a Groupon. The Groupon is good for standard tint only, and that is explained up-front. I anticipated having to pay for the first up-grade, and the up-charge was reasonable. No complaint there. One small "gotcha" was that removal of the old tint was not included. The rate wasn't unreasonable, but one should still be aware of this. I figure the Groupon still saved me $30 or so.
I found the people I dealt with to be courteous, helpful, and professional. They got the job done, and it appears to be very good. The true test will be if I still feel this way in 6 months, or if we are having trouble with the tint. But so far it is excellent. And it does have a lifetime warranty, so if we do have trouble they said we can just bring it back.
If I have any more tinting that needs doing I will come here and let them do it. If you don't see an update from me in a few months, that means the tint is holding up well and I'm happy. :-)