Personally, I'm a big fan of using VBR, Variable Bit Rate encoding. MP3 files are composed of a sequence of frames, which encodes 22mS of music (IIRC). Each frame has a header that tells the decoder what the bit rate is for that frame. There is no reason why all the frames of a given song need to be encoded at the same rate. Some sections of music are more complex than others, and should be encoded at a higher rate, and some are simple and can use a lower rate. For a given average bit rate, the result will be better than a constant bit rate.
I also like to use the LAME encoder over the iTunes one. When I get a CD, I first rip and encode to Apple Lossless format, and store that away. Then I use a Windows tool (only because I havent' found an OS/X tool) to batch convert to a set of MP3 files using LAME and VBR. I use the Lossless files with a Roku soundbridge for my stereos, and MP3's for iPods and iPhone.