I had to backup and then delete my conf.ini and confuser.ini files from My Documents\1C SoftClub\il-2 sturmovik cliffs of dover\ to get the older game versions to work again. Try that as well as deleting the cache content.
As for performance, blackdeath is lower AVG and higher Max and Min.
I redid back to back testing and here's the results at Max settings 1920x1080 4xAA.
(only 1 GPU operating as SLI is no good)
v1.05.15950 - (Last official patch)
AVG FPS 52 MAX 144 MIN 6
DX10 Alpha Patch (Prior alpha with fix)
AVG FPS 53 MAX 124 MIN 4
v.1.07.18301 - (Current beta patch)
AVG FPS 40 MAX 166 MIN 7
So clearly avg is down a lot while max and min are up.
Having said that, the game does look to be a bit smoother (was already very smooth for me though) but it's certainly a lot lower FPS in the external shots, especially on Blackdeath. The other tracks appear to be better however so its a mixed bag. Maybe it will be better from within the cockpit.
I noticed shadow popup from the trees in this patch compared to the last official and its a bit annoying!
PS if you want to go between versions keep a backup of your parts folder and rename it to keep a copy of each version.
You will also need to delete cache, and conf.ini and confuser.ini as I mentioned above as they vary from version to version slightly in someway. Remember to back your ini's up!
