The TriPorts sound OK and are decent as far as Bose products go, but I'd steer you more towards the Sennheiser HD line (the HD555s or the HD595s, specifically). For the $150 the TriPorts cost, you can get much better quality sound and richer aural experience from a non-Bose brand.
I have a pair of the HD515s that sound just as good if not better than the Triports for far less money, and while they're larger in size, they feel far more sturdy than any pair of TriPorts I've ever put near my head.
Having owned a pair of $300 Sennheisers in the past, the model I forget, they gave me two years of great audio until one day I accidentally dropped it from about 4 feet off the ground and the left speaker gave out. I was a little miffed about that. Another point was that even with the volume set at max on the iPod, audio from the headset was softer than I'd like.
I am attracted to the Bose for its featherweight feel and sound isolation. Guess it comes down to personal preference.