I upgraded to those from a pair of Shure SE110's. The shures were great headphones too, but i decided to upgrade from them mostly because I've had them for a long time and my pair didn't have an inline mic.
Apple's headphones are absolute junk, I would go with a 3rd party to get the best bang for your buck!
If you want to save a little cash maybe try the Klipsch Image series, I have heard they are great and they are a little cheaper than the Reference series!
For the money Apple charges for its in-ears, I would buy a Sony NWZ-252 Walkman as it is cordless and water resistant. This is, however, assuming that there aren't any specific iPod functions you need.
I got them a couple months ago and they're not exactly the best in-ear earphones I've tried. I'd recommend getting something else. I like my skull candy earphones more which are about a third of the price except they don't have buttons.
I don't own a pair, but the general consensus is that they are better than you'd expect for who they're made by, but still only okay at best. Good if you want an Apple-branded, balanced sounding headphone, but don't expect the last word in detail, or anything else for that matter.
The S4s are quite bassy, and are probably comparable, maybe a tad better, but still nothing to write home about.