When Altis was first released, I was easily getting upwards of 55-60fps without breaking a sweat. After the 32 bit user issues were addressed, I lost about 10fps, but it was still more than playable. Last week, however, I found myself maxing out in the mid-to-low 40s, and, today, during a simple, thrown together mission, I was lucky to get out of the teens, with dips as low as 12 fps!
My rig is an 17 2600k oc'd to 4.5ghz, 16gb RAM, Radeon 7970 3072MB. Game is running off of a standard platter, but, still, I've been getting KILLER fps on this game (and in far more intense and populated missions).