If you travel a lot by air or train, these will be a good buy. I bought mine at a US airport just before flying home to the UK, and the difference compared with the airline freebies I'd suffered on the way out was astonishing. (You'll need an adaptor to connect them to most airliner sound systems - it's not supplied but there's room for it in the neat little oval case the Shures come in.)
I found the rumble of the engines was excluded to the point where I had to listen for it, and I could get happily lost in the dialogue of the two films I watched. By comparison, through the airline phones I lost huge chunks of dialogue in the background din. The Shures also keep your music in your ears and out of other people's: coincidentally, my seat-mate had a similar pair and I detected no sound spillage at all from them.
Travel apart, if you simply want a fine-sounding replacement for your regular iPod headphones, the case is less clear-cut. I've found that the Shures sound good with orchestral and chamber music, and produce a well-defined image - the first piece I played through mine was the Sibelius Violin Concerto, and the solo instrument was very well 'sized' relative to the orchestra. Rougher, more percussive music upsets them, though - a strident guitar chord or cymbal crash can sound truly awful. The same track played through my (much cheaper) Koss Portapro folding phones sounds much fuller and happier - so much so that if I was packing for a long trip, I'd put the Shures in my cabin bag, but have the Koss pair in my suitcase to use once I'd arrived.
A final word on comfort: I was suspicious of the in-ear design but found the Shures remarkably comfortable. The interchangeable ear buds also fit very firmly onto the nozzles - fitted properly, there should be no danger at all of one coming loose and staying in the ear.