Since reading this thread, I made an order with Zenni.
I received my glasses from Zenni on Monday. Ordered a nice pair with 2 extra sunglasses clips and another complete pair just for kicks. Paid extra for the clear coating (glare resistance) on the good pair. Spent 54 bucks including shipping from China.
Everything was as-ordered, in great condition, and fit right out of the mailer, which was rather cheap but obviously did the job of making the product arrive safely. They also sent some cheap glasses cases and some microfiber cloths. What was a surprise were the glasses - which were better quality than I had anticipated. Even the el-cheapo pair I bought to keep in the car glove compartment were nicer than they looked online.
The order took 17 days to arrive. Yup, that's a long time. Then again for the price...
So what I learned:
Don't dump your local eyeglass place. Support the optometrist and the store with the cool frames - be it a specialist eyeglass place or a mall place like Lenscrafters. They have the best stuff and it does cost a bit but it is worth it for your main pair of glasses. But if you want a spare pair to stuff in the glove compartment, some cheap prescription sunglasses, or wanted to try something funky - try Zenni.
You need to have an accurate PD measurement - the distance between the middle of the pupils of your eyes. You realistically cannot do this by yourself - but can be done with a friend, easily. Zenni only deals with people who have symmetrical PD's - meaning your head isn't oddly shaped and the distance between the pupils and the center of your nose is equal for left and right.
I can recommend optometrist Terry Huseman at Merle Hay Mall. The entire staff there is very cool and they are thorough, professional, and affordable even with no insurance on my part. Next door is Lenscrafters and they had very comfortable sales staff and some great product.