Pros: built like a brick shithouse, good soundstage
Cons: isolation, price
I lost these on the train, and boy was I sad.
UM2 are good phones, the best thing about Westone is their almost legendary build quality. Make no mistake, these puppies are built to last: strain relief out the woozah, and a thick plastic housing that looks and feels tough. Westone's braided cables are also the best cables I've used; low microphonic and very tangle free.
Comfort is also great on these phones, like wearing nothing at all - especially with the supplied comply tips. However I did find - for my ears - that only the long comply tips provided significant isolation. Isolation with other tips was very average - these phones don't go very deep - and comply tips are so expensive that was not a habit I was going to get into.
Soundwise these are good, though since have been outclassed by other phones on the market. The soundstage is large and airy, and they have a lovely, warm bass to them.
A good phone - albeit a bit outdated now.