I ran the same test on my end with one of my sites, the only time that div should be visible is when someone is not using cookies. So yes you have to have cookies turned on to be able to buy something that is using flexforms.
The only reason that I have some of our sites setup on flexforms, is due to the fact that I can change the specials and run A/B testing a lot easier than with the jpost forms. For me to have another sales option on a jpost form I have to get someone from ccbill to set it up and get approval
For affiliates I would think that they like the new flexforms, due to the fact that cookies have to be on for them to work at all! With the jpost forms, if a surfer has cookies turned off, I still get the sale, but the affiliate gets no credit since it can't pull the id from the cookie
The other reason that I'm thinking about switching all forms over to flexforms, is a perception of how fast the sales page loads. I haven't done actual tests yet, but it seems that over the peak traffic of the evening, that jpost forms seem to take a bit longer to load than flexforms. I'm not sure if that is just because most traffic still flows thru the jpost forms, and once the traffic evens out on jpost vs flexforms that they will both take the same time to load or not
