Oakley M frames if you are going aero. They are the only glasses where the top part of the frame is high enough not to be annoying for the way I am positioned on the bike. I think Rudy Projest has some similar frames as well.

I have a 7 year old pair of Oakley half-jackets I use for basically all my sunny riding. If it's overcast or later/earlier in the day. I use cheap clear lens motorcylce goggles I won at a sprint tri raffle last season.

I love the half-jackets though, got them more to look cool before I started really riding, but they fit the bill perfectly. And they last

I did at the time...and I take very good care of mine. If I were to break them or they somehow flew off my head, I probably wouldn't go spring for another pair right away though. I mean, it is $150 bucks. You can certainly get by on a quality pair for 1/2 the cost (or less).

Now, if you're going for style or might wear them outside of training as well...then it might be worth it...I do that with mine still.

So, I guess it's really personal preference.

I use the Tifosi Slip. They came with 4 lenses and I think I paid around $40 for them using one of the 10% off codes from the advertisements at top. I use them for running and road biking and they're great. Tifosi also has a large selection to fit your needs.

I have a pair of Oakley M Frames that I had lying around with my Army stuff that I use for my tri bike. They're big on my face but they work.

I have Spiuk Sly Pros. They're older model glasses but great with four sets of lenses and a good fit. Right now, price is right, too.

http://www.dpmsports.com/prod02-eyewear/sly/slypro.html

I'm with you Semper. I gave hubby a pair of nice Oakleys, we were up in a Cessna and they went out the window. :-(

Recently I was running and had my last pair of good sunglasses on, I took off my long sleeved shirt at a stop light, and the sunglasses came flying off of my face, landed at my feet in the street just in time to be run over by a car turning right. Crunch.

Back to cheap sunglasses for me...

I train with a $10 pair from local bike shop. I've had them for 4 years not and they are still fine. I even left them on the roof of my car and they went flying off at 50 mph.

I do have a pair of CAT-1 glasses that I use for races. They have interchangeable lenses for overcast or sunny conditions and the lenses also darken or lighten depending on the brightness (cannot remember what that is called).

I put a tree branch through my eye when I was young and so I always wear sunglasses. A scar in there holds my pupil open, so I can't stand to be in any sun without glasses.

I have a glove box full of cheap glasses just in case, but I won a pair of Oakley flack jackets a couple of years ago and totally love them. They fit so well that I, somehow, have been able to keep them for a while and they are great for running and biking. I seriously love them. (I wear my older Smith Sliders when I'm in a pool with the kids though.) Even though I am quite cheap, I might fork over for a similar pair if these ever die.

I think decent glasses are worth it because I need them for comfort and I really have to protect the one good eye I have left. If you do go the expensive route, make sure to try the glasses on to make sure that they fit your face well.