Just what does "Smart Encoding Adjustments" in iTunes do anyway? The help file isn't particularly helpful.
I encode at 256 MP3 normal stereo, filter freq < 10 Hz.
I've tried turning smart encoding adjustments on and off but for the life of me I can't hear a difference.
The biggest difference is switching joint stereo to normal stereo, which is not a problem at 224 Kbps and up.