Trust me AI is quite different now, I'm flying Mirage3 CJ in a SixDay War campaign, I did made an Ace status in about 5-6 missions however I was extremely agressive and I had some luck, the MiG-21 kill was not so easy at all we went up we went down we turned we looped he made me overshoot him twice and I had the "green stuff" passing around my plane, finally I took him seriously and got him in a tight scissors fight.
MiG-17's are a bit more prone to turnfighting(logically as that is their strenght), but as soon as you brake off the turn and level off, they will be on you full throtthle and you will need burners to get away!
Hunters are pretty tuff too, turn like hell and will make you overshoot easily. In last mission I met 4 of them, shot 1 just barely and decided it's time to pick up my wingman and run for home.
Also what totally struck me by suprise was - THEY WORK TOGETHER
I was downright shocked when I saw a mig go into a high speed climb, thinking n00b you will stall infront of my guns, only to have another MiG close on my six going full guns on me
All in all, WOI is really awsome so far