CRM 2011 async operations table can still become large if you don’t have the flag enabled to delete workflow history. The goods news is the CRM 4.0 Async Cleanup scripts still work. They are available at:
Make sure you 1) run the script that creates 3 indexes to speed up the process first, 2) then execute the first script in the KB Article. The difference is HUGE and saves hours.
CRM 2011 also introduced a nice feature that will automatically remove the workflow from history, just by setting the flag under administration on the actual worklflow… Great new feature from Microsoft!