Did you update the firmware of the SlimX350 before you returned it?
Damn, that 550 model looks nice...I love the optical output. Funny thing is though, I have always liked how the 350 had the buttons on the side and was easy to use without the LCD control. The 400, and it looks like the 550 from what I can tell, both do not have exterior controls so the LCD unit is always needed.
Nice thing is iRiver has a habit of selling their updated LCD's seperately for the older models...

Damn, that 550 model looks nice...I love the optical output. Funny thing is though, I have always liked how the 350 had the buttons on the side and was easy to use without the LCD control. The 400, and it looks like the 550 from what I can tell, both do not have exterior controls so the LCD unit is always needed.
Nice thing is iRiver has a habit of selling their updated LCD's seperately for the older models...