Great article - we've used MERGE for some time and it reduces the CRUD burden considerably.

However, it should not be used if you are using transaction replication. We've found (and there are others if you google) that replication does not recognise the MERGE statement correctly, and will issue a DELETE/INSERT instead of an UPDATE to the subscribers. This can then collide with any Foreign Key Constraints you may have set up, breaking the replication. Unfortunately this has meant we've had to remove the use of MERGE for a lot of our routines.