Summary: After two weeks of daily use, I feel I "get" what this IEM is all about now. It's a great IEM for all types of recordings and music. I've run everything through it on my iPhone 5 (no external DAC/Amp) via iTunes and FLAC via Capriccio. I have been doing comparisons between the IE 80, Sennheiser CX880i and Klipsch Reference S4i.
There is no competition. The IE80 wins on all fronts except isolation, which I'll get into later.
Summary: Bought these after several years of using and enjoying other Sennheiser headphones, both in-ear as well as over-ear. I have been an avid fan of the CX300-ii for a number of years: simple, cheap in-ears with good sound quality, and recently took it upon myself to make the upgrade, given my enjoyment of music and growing amount of time spent travelling. The quality of their products thus far meant Sennheiser was my first choice.
Summary: Had these for about a month now and it's made listening to music much more fun. Very expensive though (hence the loss of one star) but overall I'm very happy with these IEM's - the build quality is very good and there's a good supply of earbuds to choose from. For those wondering about sound isolation, yes, it's not quite as good as I'd expected but I'm sure I could improve it with the foam tips.
Summary: I use headphones solely to listen to music when travelling with work or just generally out and about somewhere, and use a Samsung Galaxy S3 that's stuffed full of Spotify "Extreme Quality" files, and Poweramp playing FLAC (standard 16/44 and some 24/96 files). I also own a pair of Grado SR80 phones, Etymotic HF5 and previously Beyer Dynamic DT101, Sennheiser CX300 II.
Summary: I won't lie to you here, these cost a lot for dynamic IEMs but the Sennheiser sound has been so refined over the years I knew they would be a decent upgrade from my Denon 551's. Okay, what do you get for your money? First off the IE80s come in a nice card box that has a cool flap, there are various plastic trays that hold all the bits and pieces inside.