Should definitely be adjusted, at least for the higher graphics settings...

Improved in today's dev build, now around 25-35 fps average rather than 18. Still needs work though.

When flying over the airfield I noticed that the lighting seemed more 'flickery' than yesterday; rendering and then disappearing for a second in various areas.

Also, only about a quarter of Agia Marina is lit up, is it meant to be like that?

Can confirm this. 60 FPS in day and 18 at night same scene... Switching dynamic lighting or HDR to 'low' makes no difference (assume it's a lighting problem due to the latest updates).

Hope don't have to change the lighting back to how it was... It looks so much better now in towns :)

EDIT: Also noticed GPU usage was significantly lower at night.

No longer having this issue, thanks :)

This could in fact be an issue with the Steam overlay and not specifically the 'End' key...

Don't mind smoke going through walls, happens in every game. However, as someone suggested, make it unaffected by wind when thrown indoors and form in a shape similar to the smoke seen in (dare I say) CoD or CS. This will make smoke more effective in indoor environments and reduce the amount of clipping because of the shape.

Shooting out lights is possible, but it takes way too many bullets.

You can change this for heli's. Go to the flying movement (might be called vehicle movement or something) part of your controls menu, and switch the 'mouse up' and 'mouse down' controls.