I have an instance of SSRS 2000. I want to move the catalog DBs to a SQL 2008 R2 instance. A few months down the line, I'll upgrade the SSRS instance to 2008 R2 as well. Will SSRS 2000 work ok with its DBs sitting on an R2 instance?
I would recommend testing it out on a development or test system. A side by side migration is fairly straight forward and provides a quick rollback plan. The article below should get you started.