I must have been sleeping under a rock, but when did “Upsert” become a word? It refers to the combination of insert and update statements for a RDBMS. What it means is: add the row it does not exist, otherwise update the row using the primary key.
It would be cool if SQL Server had this feature. There have been a few times where it would have been useful, mainly with batch operations. In those cases, I wrote stored procedures to handle upsert operations. At the server level, it should be trivial to implement an upsert statement as opposed to manually coding it in SQL.