In-room speakers are always sort of the defacto choice. Wall-mounted speakers represent a likely compromise, and in-ceiling speakers even more so!
Basically if you CAN use regular tower or bookshelf speakers, then that is the choice that most of us would find the most comfortable. But if you are seriously limited in terms of placement, then towers or bookshelf speakers aren't always the best choice. If your speakers are going to be crammed right up against a wall or two anyway, then you might as well look at speakers that are designed to go right up against the wall!
Paradigm, RBH and Focal offer in-wall and on-wall speakers that I quite like. Paradigm's Signature on-wall speakers are very good, and not too picky about placement, but they are also expensive! RBH's selection of in-wall speakers are impressive, as are Focal's, which can also be wall-mounted with their back-boxes.
In-ceiling speakers should not be used for any front channels and should only be used for surround or surround back channels when you have no other option, IMO. They're an OK compromise for surround duty, but I'd never ever use them for the front three.