I haven't done this with hotel stays yet but I'm sure I could. I occasionally do this with flights. It's a no-brainer to use 25K airline miles instead of $1500 in cash for last-minute domestic coach trips. My employer is more than happy to let me monetize my miles in this way since the out-of-pocket cost to the company is the same.

The problem is that SPG points are much more valuable than airline miles and I have fewer of them so there aren't nearly as many slam-dunk mega-high-ROI arbitrage opportunities for monetizing SPG points.