I think the "flat" ones you see the big name guys use are typically custom molded to fit their ears. If you're looking for nice quality, off the shelf in-ears, however, I can personally recommend Shure SE215. Of course, as Mike said, in-ears are typically wireless, therefore, EXPENSIVE. The Shure PSM200 is a good wireless system that comes with the SE215s standard. It can be used wired OR wireless.
If you're in a studio or old guys like us who don't move around much, wired might work OK for you. We play seated on stools and found we can run the in-ear cables up our instrument cables with no problem and they aren't ever seen by the audience any more than the instrument cables are. For 3 of us, that little inconvenience saves us about $1500!!!!