id3 tags are only difference therefore....
 

Since sometimes the only difference between some mp3s are the id3 tags, it would make sense to clump together all peers with the same mp3 (minus the id3 tag), and then add the id3 tag on at the end.

This would make search results a little tighter, and performance a little better.

This is something already done in Shareaza, and I assume, it will be in LW someime, but it poses the problem, that Metadata then needs to be transferred via the serch results or in some other way, and any Metadata, which your program doesn't understand will be lost.