Yup same here as well as clouds.
The sad thing about clouds is, it's a realism setting, they actually influence the aircraft negatively when you fly through them performance wise, make your instruments go nuts if you don't have or turn on your pitot heater and of course the pilot with reduced visibility. So it's really desireable to have them on if you want realism.
But on the upside the clouds as well as the whole graphics engine are still not final, as Luthier stated in the future plans, with a reworked graphics engine we should experience a 50% performance increase.

I am experiencing the same problem with ground dust, less with smoke from burning aircrafts or crashed ones, but no problems with clouds (losing around 5 fps, not that bad).
My rig is in the sign.

Maybe some particular setting in my AMD Vision Control Center ?

yes for me too...look at performance threads...

Effects setting issue
 

The main driver of this problem could be the "Effects" setting value in the Graphic Options in the game menu. The difference between "medium" and "high" is almost inexistent. The FPS impact is quite high in very specific situations with both settings. Setting this value to "low" will solve the problem of FPS impact the easy way. That is the total absence of effects, no dust, no smoke, no explosions, no fire, no nothing....

Not even high end GPUs are able to handle this elegantly at this stage of the game.

We must all consider that the reference for a good graphic setting evaluation should not be the recurrent low level flight over London, since this situation (INHO) does not add much value to the game. We should consider the “Back death” track as reference, with a significant amount planes, multiple combat like situations at different levels, ground pounding, fast view/camera changes.

Most of you will find out that being able to fly smoothly over London, while playing the “Back Death” track, will still suffer from dramatic FPS lows (<10 FPS) specially during explosions, flying around smoke columns, fires and so on.

Being such a specific issue, one tends to think that it would be relatively easy to optimize, but what do I know?
We will see.

Salutes Majo.

Not really noticed any significant drop in fps with dust and smoke EXCEPT when there's a massive fireball from one of the large fuel silos going up.

PPP

Triple 2.3ghz processor, 4gb ram, hd RADEON 4800

nothing to do with the systems...I have i7920 OC 3.5Ghz, GTX470 TF2 OC to 790MHZ and 6GB of RAM and have slowdown near effects (dust etc..)

no
i have them too
is totally an fps drop down killer

A thing that dissapointed me in the last patch was that nothing had been done about it, I'm sure it would make a great deal of people happy if it was sorted

Tav.. there is a hundred or more different things that need sorting and nothing was done about them either..
There are probably several hundred people that are dissapointed right at this moment but for different issues.
Why is it when a patch comes out the majority on here seem to set themselves up for a fall?
I'm just happy that I can actualy fly the damn thing.. there you go, something positive for a change! :)