My biggest gripe about ID3v2 is that they're at the beginning of the file. With ID3v1's being at the end, you can remove them from a file while it's playing and it's trivial to do so and very(!) fast. I wrote a tiny C util to remove ID3v1s (before v2 was around) because their short fields made them worse than having no tag at all. So with thousands of songs without any tags, I don't like having the occational ID3v2 slip in there. Removing v2 tags is a pain since you have to copy the whole file. It takes a long time and you can't remove it from the file you're playing.

I'm sure very few others share my complaints.