Nice article. Your numbering system needs alignment (starts off zero-based and moves to one-based in the results table).

I would be interested to see whether the final 'staging table' option would run even faster if it was indexed just before issuing the UPDATE.

Another technique I have seen used is INSERTing all rows (inserts and updates) directly into a flat view of the table (create view as select * from table) which contains an INSTEAD OF INSERT trigger which performs a MERGE. The good thing about this is that, by tuning batch commit size in the SSIS destination, you can achieve a near-continuous data flow. Might be worth a test ...