>Of course all the processing has to occur within the transaction, and so it makes no sense to me to use them. But, it is valid. Weird.
<

You are absolutely correct here since any existing records involved in a Tx are unavailable until the Tx is either committed or rolled back...

I think it can be summed up like this:

1. Always use buffering
2. If you have situations where all multiple updates have to be successful,
use Tx's in addition to buffering...