MP3 Diags
This kind of program needs a lot of screen real estate, so I recommend the main window to be at least 1200x800. Probably it's best to just maximize the window (which is the default behavior.) If your screen has a smaller resolution, changing the fonts should help you cram more information in the little space you have.
I made the decision to use ID3V2.3.0 instead of the newer ID3V2.4.0 because I didn't like what I saw in some 2.4.0 files (invalid fields that some tools create and others expect to be invalid.) Also, I couldn't get my Archos Gmini 400 to display images stored in 2.4.0
Future plans
Based on feedback, there will be a final release 1.0, after which minor changes may get implemented in 1.0.01, 1.0.02, ... Currently the focus of the release 1.1 is disabling UI elements that don't apply in a given context. This might change (again, based on feedback.)
I'm considering a different labeling and color-coding system for notes, where you have a different color for each of the 14 note groups, to make it easier to tell which notes are related. Also, the distinction between errors and warnings isn't always obvious, so I'm not sure how useful it is.