There are a few basic questions to ask yourself:
1) Do you want multi source as well as multi zone (i.e. play different things in different places)?
2) Do you want to avoid running wires at all?
3) Do you listen to internet radio?
4) Do you only want to listen to a music collection stored on a hard drive, or through other sources as well?
5) Do you want to do this yourself, or just buy a plug 'n' play system?
#5 really is the determing factor, if the answer is just plug and play, no wires, hit all sources (or almost), then probably Sonos, although Logitech also puts out some decent products I hear.
If, however, you do not want multi source, and you may want to do stuff on your own. Well then you can buy a relatively inexpensive refurb stereo receiver, a speaker selector, impedance matched volume controls for each room, and assuming you have itunes music, an airport express. You can use an ipod touch, or iphone, as a remote for such a system. The downsides are running the wires, and that you have to play the same thing everywhere.
I've been looking into doing the same thing, that is what I have learned thus far.
