Linda Epstein named the Ultimate Ears Super.Fi 5 Pro the TabletPC2.com product of the month. As James points out, it's saying something to be considered an "excellent value for the price" when these earphones cost a whopping $250.
If the $250 price tag scares you, I would strongly recommend checking out their Super.Fi 3s which retail for under $100. This may still sound like a lot to many of you, but believe me they are worth it. The value is even higher on these given the price. Unless you're a real audiophile, you'll probably see diminishing returns on the $250 super.fi 5s (that is, you probably won't think the 5's sound 2.5x better).
I was originally considering the "cheaper" Etymotic or Shures, but a recommendation through a friend turned me on to the Ultimate Ears. I couldn't be happier with the purchase, and I really prefer the Ultimate Ears sound over the other two.
$80-100 may sound like a lot for earphones, but they are well worth it. The improvement from a cheap $20 pair to a $50 pair (e.g., like the Sony Fontopias I used previously) is somewhat marginal. The Fontopias are not even in the same league as the Ultimate Ears though.
Using these headphones, I've quite literally heard things in some of my favorite songs that I've never heard before. They are quite comfortable to use for extended periods of time and are really good at blocking out noise which make them wonderful for commuting on subways and buses.
From what I understand, the UEs are also the only pair where the earbud itself separates from the cord for easy replacement. This is important as the cord is both the cheapest component to replace and the cause of most problems.
And despite being what appears to be a relatively small company, their customer service is top notch. I've had some issues with the sound quality recently, and they first sent me a new cable and have since replaced my earbuds. (Well, I've sent them back, still waiting for them to come back).
I've since recommended them to my father and he's a huge fan as well. He was initially concerned with the in-ear style, but he too seems to find them quite comfortable.
Highly, highly recommended.