I was never really satisfied with the above code as it was very rushed and as already stated written with much Guiness being consumed, however it met my needs at the time...
After reading Test-Driven Development in Microsoft .NET as recomended by our own Nerseus I felt it was a good a topic as any to try and put the techniques into practice.
So far it only supports v1 and v1.1 tags (2.0 is a big leap forward - but may happen in the future). The library is written in C# as are the included tests, there is also a very basic UI written in VB.Net (I didn't realise I was using VB until I had pretty much finished the front end and couldn't be bothered doing it again in C#...)
If you want to run the tests yourself you will need to obtain a copy of NUnit and the test mp3s can be obtained Here.
In a debug release it will compile 'as is', to do a release build you need to provide a strong name key file - path is in the assemblyinfo.cs. If you use the link to the above test files you can edit the path to them in the MP3TagTests.config file.
I do intend to continue developing this to support v2 tags but will probably continue development with VS 2005 as this will allow me to take advantage of generics to manange collections of frame types and also an easier time with the improved IDE (refactoring and intellisense improvements). MP3Tags.zip