The one feature I miss the most is an inbuilt note feature in bnet. After each game you could write a note about your opponent (cannon rusher, 3-rax proxy cheeser etc).
The next time you played the same opponent your old note about that opponent would automatically be displayed.
It is a easy feature to implement and would make laddering a more enjoyable experience. Plus it would have the upside that people that rely on a single cheese strategy would eventually be hard countered.