It really depends on age & condition of duct cleaning pittsburgh. If they are dirty,dusty etc it just recirculates the dirt into your house when heat comes on.
Then absolutely get them cleaned, with forced air I think professionals are required. They've got the tools to get it done right.
Get a second estimate & or ask the local company offering service for references from their customers, how long they've been in the business & what kind of guarantee they offer.