I can confirm that the CHECKSUM (and or CHECKSUM_BINARY) approach works a treat.

It possible to create a generic sp that will work for any table with suitable pkeys defined, allowing you to check for updates and apply logic only where necessary.

Obviously you don't need to use CHECKSUM when looking for inserts or deletes.

Using triggers to keep a audit of changes should work just fine, but I suspect will lead to a more complex and less robust solution. Depending upon the usage levels of the tables (i.e. lot of updates/only a few updates per sec etc.) however, the overall processing effort may be lower using triggers.

If you use the CHECKSUM approach (for updates) and IN's and NOT IN's for inserts and deletes, expect the nightly job to take some time if the tables are large.