I've made a few important corrections to Tip 15.

I've corrected the bit that said the UPDATE SQL includes original values of Updated Properties in the WHERE clause.

At the time I was consciously attempting to simplify things a little, but as Tanveer and Danny highlighted its not really a simplification if it leads to confusion.

Mea Culpa!

At the same time I've fleshed out the caveats section a little more.