I've gotten a total of five pairs of glasses from them, three regular pairs for me, one for the fiancé, and one pair of sunglasses for myself. I love them! I had the same pair of $350 glasses since about 1995 and in 2005 one of the nosepieces broke off, leaving me walking around with a missing nosepiece until the end of 2008. At such a high cost, glasses were never a fashion option until I discovered the joys of online optics. :D
I got a test pair, $8 frame, thinnest lenses possible (1.67), very lightweight on my face (this is a good thing!) and all around perfect:
In the next order I got two for myself. The first one is an art-deco style, stainless steel frame, around $45 with the thinnest lenses I could get, 1.67:
I love them a lot but I don't tend to wear them unless they go with a certain outfit. They're a bit heavy because of the metal, very sturdy. The pair I constantly wear now is tortoiseshell, a bit on the cat-eye side, around $37ish I think, because I got the lenses thinned a bit at 1.61.
Sunglasses were surprisingly inexpensive. The frame cost $8, a few bucks more for tint and shipped I believe the total was $17 shipped... for prescription sunglasses! I didn't bother to spend more for thinner lenses on these, they're 1.57, which is why it was so cheap. I have a fairly strong prescription, too, but the chunkiness of the frame hides the thickness of the lenses quite well so it worked out.
I'm very happy with the ones I've gotten from them. :)
If you're thinking about getting online glasses, for the price, I really wouldn't hesitate. Just make sure your optician gives you your PD (pupillary distance) measurement. FYI, I know some people don't like them but the opticians at Walmart can do this for you. If all else fails there are instructions online that tell you how to measure your own PD, but I'd say that's a last resort as I believe your optician is obligated to tell you your PD measurement if you ask. Don't quote me on that though... I'm not sure if it varies from state to state. I'd also recommend going by your current pair of glasses and not really deviating much from those measurements, which can usually be found on the glasses somewhere, probably on the nose piece or inside of the arm. If you don't wear glasses currently, I'd recommend trying on frames wherever you can and noting the widths (nose and total width) and arm lengths that fit your face well, just as a rough guide.
Shipping from Zenni has always been quick for me but I know some people have had issues where it takes longer. I've always gotten my glasses within a few weeks of ordering, which I think is perfectly fine as I wasn't in a hurry. I can't vouch for other online services but I'm sure they're all pretty decent. Check out this blog for more info:
http://glassyeyes.blogspot.com/Sorry, I didn't intend for my post to be so long, but there you have it... good luck!