played the first mission of the GB campaign like 3 times in a row on various settings was playable on max with 1x anti-aliasing although heavy shudder when it hit
played again on medium settings (default) still with 1x anti and again was playable slightly better fps and a pretty heavy shudder but hit less often.
then again on everything low setting except for debris and aircraft model slightly better fps and far fewer shudders but still big when they hit some were lasting like 6-10 seconds.
todays testing was was geared on finding out (still guessing really but an educated one at least

) weather or not my rig will be able to run this game at full max settings after its tweaked and i believe this is a solid yes.
i even followed the river rite through the middle of london with max settings and the fps was probably 10-15 (full on slide show) plus the 10 second long shudders but i was still able to follow the river through town.
If this is the performance using 32 bits, 1 core, 1 or 2GB ram and not even all of one of my video cards to run then i am a very happy camper at this moment