Puhlease.... DEN has less delays than ORD. I do agree that 30 minutes is a tight connection, but it is definitely makeable provided there are no irregular ops (or other delays). If you are comfortable with the risk, then it's fine. If you are not comfortable with the risk, try to find a longer connection.

One possible snag is that DEN is using the A and B terminals for flights with no real rhyme or reason to it (A used to be exclusively TED) and this can add several minutes to your gate-gate travel time. My parents had a 45 minute connection last friday in DEN with the inbound flight being 5 minutes late and still made it from the B to A gates before their outbound flight was boarding (including a stop at the restrooms) so 30 minutes is plenty of time to get between gates.