I think i read an article on Cracked.com about this a while ago. I think paying for a brand name on the side of your glasses is not a great idea, buying quality brands may be a good idea.
I wear glasses everyday, all day (except when sleeping), and having a comfortable pair of glasses that fit correctly and stay that way is important. I don't shop by brand, I basically just walk around and try on pair after pair until i find the right ones. I think the last pair i bought took me about 4hrs and 5 different stores. In the end, the pairs that seem to look the nicest and fit the best tend to be the "designer" frames.