Let me explain what I've done on a couple of occassions and how this has worked for me...

I work for a large financial institution (primary job) that requires us to use a vanilla in-house Visa card for T&E expenses, and I also have a business Amex Platinum charge card tied to a small business in which I'm a partner. Often, when checking-in a hotel on business for my primary job, I tell them that my assistant booked the reservation under the wrong card, and then hand them my Amex Platinum. At the same time, I ask for a "decent room" (sly way of asking for an upgrade).

Two out of two times this has scored me a suite, once at the Mandalay Bay in Las Vegas and once at a Ritz-Carlton. Before leaving, I switch the charges back to my corporate Visa (which is necessary if I'm going to be reimbursed by my primary job).

It's almost as if I'm getting an upgrade due to the Amex--perhaps the hotels are accustomed to upgrading people with this card--without paying the high FHR rates (my company's rates are usually half of FHR, particularly at Four Seasons and Ritz-Carltons).

Has anyone else ever tried this?