+1000 on these.
I started using these a year or two ago at the suggestion of a guy on KLRWorld.com. Hated the idea of dropping so much $$ on earphones, but I couldn't be happier with them. They block out almost all of the wind noise but you can still hear important stuff if you don't play your music too loud.
There is a pretty heated debate about whether you should use earphones or not. I'm firmly in the camp that they are safer than not using any ear protection as long as you don't blast your music at full volume.
I like these particular earphones so much that when I lost my set (and Ipod) I immediately ordered another set. It hurt the wallet, but I'm addicted to them. If I ever get caught in a situation where I have to ride without them, I don't feel right now. It's like riding without gloves or something. It's possible to do, but it just feels wierd.
After losing that set, I did a lot of research into other options for the replacement set. I looked at ones more and less expensive. From what I found, you can find better earphones for more money, but you'll have to go quite a bit more money (like double or more). The ones that are just a bit more expensive don't seem to be a good match for motorcycle use (read: stick out too far from your ear). These are the best match for ear isolation, sound quality, and fit deep into the ear so they don't conflict with helmet usage.
Did I mention that I like these earphones?