There is also discussion on the LARTC list at the moment - someone called roy has rewritten IMQ but still sees crashes. He thinks they are related to locally generated traffic, so IMQ for ingress should be OK.
He just posted this, thought it may be of interest.
Finaly I made imq driver stable it did not crashed for all 5 hours under high load, soo looks stable. (old one was crashing after 1-5 min for me)
no need to patch anything just compile and insmod, should work with any kernel probably must be > than 2.4.20
This is completely diferent code than old imq. you can find it on my server http://pupa.da.ru please tell how it works for you and how stable it is.