I use an app on my Mac called Fluke to enable playback of Flac files, wondering if there is a similar hack/app that would allow Flac playback in the stock iPod app and also the ability to sync Flac to iDevice through iTunes?
To my knowledge theres no such file, but its recommended to convert to mp3 then sync in order to save disk space.
I have about 27gb's of music on my iphone and about 40% used to be flac before I converted them to mp3. Theres definetly no sound difference on the iphone since the speakers arent production quality, so mp3 is your best bet.