This is not an existential question, but a very practical one. While it won’t apply to all your music, you might want to consider doing so for certain CDs.
Here’s what happened to me. I was listening to a recording of Bach’s Goldberg Variations by Robert Hill this morning, and noticed that there was a tiny hiccup between the tracks. With iTunes playing music gapless, since version 7.0, this shouldn’t have happened. But I suspected that it might have had something to do with the ripping: I had originally imported this CD under iTunes 5, a couple of years ago.
I thought the problem might have been in the original ripping, so I tried importing it again, and it plays fine. So, for some reason, even though iTunes “updated gapless playback information” for these tracks when version 7 came along, it didn’t do so correctly; or the actual rip was different back then. In any case, if you notice any problems like this, you might want to rerip the CDs that don’t sound perfect.