Bottom line on this, as with most upgrade-related issues, is that it all depends on who is working behind the front desk at any given time. In contrast to the Southwest Hilton Houston anecdote above, I recently stayed at the SW Hilton and got upgraded to a suite. Likwise, I recently stayed at the Westchase Hilton in Houston and got upgraded to a Penthouse suite. However, I've also been in the same position others above reference - begging for an upgrade at an empty hotel and getting zip.