I personally use FLAC because I like the ability to add metadata. While I understand that some may not value it much, I like to create playlists using genre and my personal ratings. For instance, I can create a playlist of just my favorite prog rock tracks selected from my 13,000 track library to transfer and play on my iPhone.
A program that hasn't been mentioned is MediaMonkey. MediaMonkey has replaced Foobar as my main media organizer/player/streamer. It plays most audio formats (wav, flac, mp3, ape, ogg, etc.), has lame and flac encoders built in for ripping, converts formats on the fly, has DLNA capability, and is one of the best media organizers around. It even organizes and plays my MCH flac files ripped from DVD-A's.
One of the features I rely on is to convert flac to mp3 to store on my iPhone and iPod. I simply select the flac files I want to transfer and the encoding quality, and it will transcode from flac to mp3 as it copies the tracks from my pc to iPhone/Ipod. I have a 160 GB iPod with all of my stereo tracks at 256 kbps mp3, plus various playlists of favorites, while my 32 GB iPhone contains mostly playlists of favorites. The type of playlists that can be created is endless based on embedded metadata.
To stream, I use MediaMonkey's DLNA media server to either serve the flacs (stereo or multichannel) directly to my Oppo in the theater room, or convert to mp3 on the fly to play on a PS3 in the family room. Again, with the playlist capability, I can stream by genre, artist, rating, year, etc. or any combination of the above. Over the holidays, I was streaming Christmas favorites to my family on the PS3 in the family room, while I was listening to a playlist consisting of my MCH Porcupine Tree albums streamed to the Oppo in the theater room.