I have to say, the Su-26 is brilliant fun to fly. I've noticed at least one bug with it though, although it's only minor, but the pitch lever in the cockpit doesn't work. I can adjust pitch with the axes assigned, but if I try the clickable one in the cockpit the lever moves but it does nothing to pitch.
Otherwise, I'm also unable to change the loadout of it in the normal quick missions (although I can't remember whether this has always been the case with all aircraft). I can't add guns to the gun racks or select a pre-saved loadout.
I've tried the wonder weapons in FMB though and they are good fun. With regards to the AI not engaging properly though, if you put them on free hunt, they engage. I found out the hard way, with 36 109's all shooting at me at once
The poor Su didn't hold out too long. Great fun and good for aerobatics though!