I have an iAudio G3 - solid state 1GB. I picked it because it was cheap, it plays oggs, acts as a USB mass storage device and runs on an AA battery, not a proprietary one. I can't update my firmware from Linux, and I don't believe anyone has hacked firmware. As mentioned earlier, it lacks gapless playback. It's spontaneously rebooted maybe three or four times in six months of continuous use.
From my experience and reading the iAudio forums, I have a good impression of iAudio's players in general.
Oh, and my iAudio has color sound. i mean who else has got that. omg teh w00t.