Shure's SE535 (the letters after the model number are to determine color) has been a favorite, in one iteration or another, since early on in the IEM world. It's a fantastic performer with tremendous isolation properties and the whole spectrum of sound that once comes to expect from Shure.
We consider it a deal at it's price point. If isolation and great sound are paramount, start here.
Engadget says, "If you're getting into the high-end monitor market for the first time, though, the SE535s need to be on your short list."
Here's a little something more specific from Shure