I am using the tiered pricing module and noticed that if a user is part of more than one group, no tiers are returned by the by_user method of the PricingTierManager (in satchmo_ext/tieredpricing/models.py)
This is because the PricingTier objects get filtered in the sense of group = group1 AND group2, etc, when it should be OR.
I have attached a patch that I used to solve the problem.
Andrew Cressman -
PeaceWorks Computer Consulting Inc.