One of the things I love about roll20 is how fast it is. This is great because I have players with terrible connections playing from places like iraq or alaska. Most my friend whom I used to be able to gather around a coffee table are now overseas or far away. This is why we need a VTT.
We have tried other solutions and they have worked well enough but we always ran into the problem of unstable connections. As connections dropped, lagged or flustered we would have to wait for players to reconnect and download all the material again. This was frustrating at the best of times and hindering at the worst of time. We even ended campaigns because of frustrations over the connections.
Roll20 solved this problem. While I don't really like how a lot of things work the one thing roll20 does better than any other is being in the browser. This means that internet problems are usually fixed by a simple hit of F5 (refresh) and don't require relaunching (or waiting through a crash) a program simply because of your internet connection.
Now this isn't true. Internet problems require 15 seconds of load time, at a minimum, and that isn't really acceptable to me. It doesn't seem like it but it adds up. One of my players disconnects from the internet on average 10 times per game. Normally it isn't on his turn and he doesn't mind missing some combat so it doesn't so us down. Now those otherwise short breaks in his visibility of the game turn into two and a half minutes of waiting for an ad.
Yes, I think the sponsor system is great. However if I am going to put money down on something it should be because I love the service not because I hate a part of the service and want it removed.
--- WITH THAT OUT OF THE WAY: HERE IS MY SUGGESTION
Please do not load adds if the page is simply being refreshed. The only reason people are refreshing a page because something went wrong. One should not be forced to look at the same ad over and over because of bugs.