If you're interested in having FSAA active in M&M 9 without the horrible-looking 2d grid-line effect layered over every 2d portion of the screen, then it's very simple to get it: simply uncheck the option for "optimized surfaces" in the video options settings and then force your level of FSAA from your GPU driver cpl. 8xFSAA EQ looks really nice in the game when set from my Catalyst cpl (13.12WHQL). When the option for optimized surfaces was put into the game it was originally to get all of the performance out of the game that was possible. (The Catalysts also have a cpl option for "optimized surfaces" which I turn off and leave off because it slightly degrades the image quality of some texture surfaces in order to stimulate better gpu performance. While this was somewhat helpful for performance when M&M9 shipped, it is pretty much meaningless today, and especially in a lightweight game like M&M9, because gpus are generally far more powerful than they were when the game shipped. Image Quality improves and then rockets up when FSAA is applied, and any performance loss from deactivating the option is virtually non-existent today.)

At 800x600, especially, robust FSAA really helps the image quality of the game and I thought it was a shame to have to lose it to the 2d gridlines...:/ So I disabled what I think is the most useless gpu option in the game, and--viola! End of the checkered grid-line effect when forcing FSAA! Hopefully, you'll get the same result I got. BTW, am also running Akrose's terrific "Border Fix" for the game that allows it to run fullscreen instead of in a perpetual Window!

Also, one last detail that may or may not be of importance regards this issue: my original GOG copy of the game was the 1.x installer version I downloaded when I bought the game. It didn't want to play nice with Win8.1x64 at all--regardless of the compatibility modes I set. But just today I installed the updated GOG 2.x installer version, and it ran under 8.1x64 the first time I tried it--and I noticed that it runs from a different launcher altogether than the original 1.3 version of the game I downloaded from GOG when I bought it. All it's doing is running the admin mode and anti high-dpi scaling compat modes--runs fine with no OS compat mode selected at all! (Running from mm9.exe doesn't want to work nearly as well if at all under 8.1x64.) Great compat fixes for Win8.1x64 in the updated game release!

Anyway, upshot is the game looks far, far better than it did sans FSAA, and under Win8.1x64, too! (GOG just seems to be getting better every day!)

Edit: Wanted to add that in order to force FSAA in the game with the AMD Catalysts, the file to choose to apply the FSAA & AF settings to is "Lithtech.exe." Using the mm9.exe file or the new launcher exe will not work, in case someone isn't aware of it. Also, I'm running the game under Win8.1x64.