I'm using BubbleUpnp on a Droid for the client controller. I haven't found an iPhone program that is anywhere close to useful.
I use iSedora for a server. I haven't restarted it once or had any problems with it.
The PWD Bridge disappears from the net occasionally (the client ends up picking a different renderer), and then eventually hangs. 24hrs is the longest I've made it I think. Bah humbug those software people!
A MacBook Air is awfully tempting. I could at least drag my whole music collection around with one of those. And I could search, sort, have album art, gapless playback, etc. I'm re-talking myself into it as I type....
So pretty much any kind of server option ends up being clunky, that is, if you get it to work at all.