The first thing I noticed when I put them in is the fit. Klipsch really did do it right, the "contour" gels (it means they are oval-shaped) really do make a difference. I'll compare the experience to my V-Modas when I first got those. Their gels were a more conventional round shape.
The V-Modas, upon first putting them in, were pretty bad. They were uncomfortable and slid out a lot, and while the isolation was alright, it wasn't perfect. It took a whole week for my ears to "get used" to them. However, the Klipsch 'phones fit great as soon as I put them in. The medium-sized gels that were on them when I took them out of the package seem to be the best ones for me. One thing that makes a big difference for me is that my right ear doesn't seem to mind these. For some reason, I could never get a comfortable fit or a good seal in this ear with my old headphones. The Klipschs pose no problem at all, isolating and fitting into both ears just fine.
As for the sound, I'm not gonna say a lot since they haven't broken in yet. The high highs aren't nearly as sharp as they could be and the bass is kind of fuzzy, being present and sort of overbearing but not very well defined. I expect this to smooth out as they break in. Despite this, they're still nice to listen to. They do image pretty well, which I like. I might post again after they've done some breaking in. They do leave a good first impression, and even if the sound wasn't going to change much from how it is now I wouldn't be too disappointed. They still sound much better than my old pair and the great fit is a big plus for me.