Comment 1 for bug 920823

According to Thomas who implemented the custom queue code, it was added for two reasons:

"1. the singing code does some checks on queue[-1], which is really expensive with compositequeue. 2. len() is also really expensive so I added a size attr - the conflict resolution is simply to keep size sane."

If it makes instances hang, that obviously sucks, and we should look into getting rid of the custom code if that fixes the problem. And no longer use queue[-1] or len() then in S&D code.