A couple more reasons NOT to go all the way to 0dB:
1) You want to do all your editing (including normalization) in the highest quality sample rate and bitrate, and levels can fluctuate in the resampling and bit depth conversion processes. If you normalize to 0 and then resample/convert bit depth you may end up with some clipping.
2) The MP3 encoding process can change the levels too, so if your recording is ever going to be converted (via the LMA or whatever), you will probably end up with clipping if you go all the way to 0dB.
Usually normalizing to anywhere from -0.2 to -0.5 will leave enough headroom for all this stuff, and like the others have said, won't really affect the perceived loudness