Whats worse, is these game applications are actually going to get an actual FPS a lot lower then 85!
Actually, what happens if the framerate goes over the monitor refresh rate is that shearing effects occur. Frames get rendered while the monitor is in the process of drawing a frame, so a portion of the frame rendered is the previous frame and a portion is the next frame. If the framerate is high enough, this isn't so bad, but nearing the 30 mark, this effect can really detract from a gaming experience. (Especially with 2D since in 3D games, movement by perspective doesn't usually change so dramatically.)
Also note that when vsyncing, if the framerate drops even slightly below the monitor refresh rate, the framerate gets chopped in half! (So if the game can't handle 85 but can handle 82, you won't get 82, you'll get 42.5! The next down would be 28.3333, then 21.25, etc.)
Or lets say you design your game specifically for 85, but the person playing it has a refresh rate of 100. In this scenario, that person will only get 50 FPS!
Vsyncing is best left to real-time engines. If you do it in a fixed-time environment, you also need to incorporate frame-dropping in case the user's system doesn't exactly match the rate the game wants. (IE: In my game PixelShips, there's a brief moment at startup where it detects the monitor refresh rate. The game is designed for 70 FPS. If the monitor refresh is 70, the game times by vsyncing, but if not, it goes by an Allegro timer instead and doesn't vsync.)
--- Kris Asick (Gemini)