In 10.6.0.40, tracks ripped to MP3 format use ID3 v2.2.
This would also apply to any tracks that iTunes converts to MP3.
This is the same version of ID3 that iTunes has been using for a long time. It is a little surprising, since most of the industry, such as Amazon MP3, moved to v2.3 years ago. iTunes will of course play them just fine.
iTunes does have the ability to convert ID3 tags to a different version, up to v2.4. You can do this by right-clicking the track and choosing "Convert ID3 Tags...."
Let me reiterate what you wrote just for my sake. So, you are saying that iTunes 10.6.0.40 can read the lastest ID3 tags (v2.4) but when encoding new music from CD or coverting formats (alac to mp3) it will only write in v2.2? Am I understand this correctly? And what this about "convert ID3 Tags..." So, when you right click on a track and click covert tag it up-converts the current ID3 tag to v2.4 or convert any ID3 version to v2.2 (e.g. v1.* to v2.2, v2.3 to v2.2, and/or v2.4 to v2.2)?
I checked several of my recent MP3s that were either purchased (Amazon MP3, Eclassical.com, etc) or were output from audio programs using default settings, and they are all using v2.3. The only ones using v2.2 were ripped or converted by iTunes.
Yes, all of the above play fine in iTunes.
I did not see any using v2.4.
Yes, the "Convert ID3 Tags..." command brings up a dialog that lets you choose one of several levels, or "None."