Originally Posted by BigE

Gift cards are not a good deal for the risk averse or paranoid. They are not a good deal if you don't think you'll have many Marriott stays in the next 2 years. They are not a good deal if you are the kind of person who easily loses track of things. If you owe money at high interest rates, you're better off just paying that down.

For the rest of us, they are a GREAT deal at 20% off. I've bought them many times before at this price and it's worked out very well. My plan is to buy gift cards according to what I plan to spend over the next 2 years or so.

RedSun's list is accurate, just overstated a bit.
1. Loss of flexibility. Just don't buy much more than you had already planned to spend anyway. If you never stay at Marriotts, then this GC discount is not a sufficient reason to switch.
4. Limited usability. I was able to use gift cards at almost 100% of the Marriotts hotel I stayed at with flexible rates. I even had luck several times on prepaid rates (but you can't count on this). There were a few cases where it was a hassle, though (long wait, confused looks). There were also 2 cases (out of maybe 30) where I had to ask Marriott Customer Service to fix the problem after the stay. They did. There is a list of brands that do not accept gift cards, but it's such a negligible % for me.
6. Bad exchange rate. Those of us who have actually used Marriott gift cards have not had a problem with exchange rates. Quite the opposite - I was often left shaking my head at how I got such a good deal. I believe you're actually SAVING money by using gift cards. If you pay with a credit card, they are shaving off up to 1% or so. The gift card exchange rate is at fair value (in my experience), almost always better than what I get with CC or at the best cash exchange place. I compared.

P.S. We all have different considerations, but I have always figured that I needed a 10% discount just to factor in RedSun's list and "break even". There's also the hassle - it often takes an extra 10 minutes to get them processed.