Steve Stedman wants to see how far behind transactional replication is:
Working with Transactional Replication with many of our SQL Server clients, one of the big questions that we are always asking is replication keeping up? Recently when deleting a few hundred million rows from a large table that is synced with transactional replication, I needed to programmatically check how the distribution was keeping up. The one measure that indicated that things were behind was the subscriber undistributed commands tab in the replication monitor. When the number of commands waiting to be applied was too large, I had to slow down my delete process.
Click through for an easy script. The really frustrating part is that transactional replication is easy but answering the same question with merge replication is a royal pain.