I think 1.10 or 1.05 is the best for me. 1.09 was actually a great one too with AHV because that has completely changed the game for me as well.
I remember playing the beta and being completely wowed by the tracers (compared to warbirds). I can't remember off the top of my head if the control surfaces moved in wb2 but i also remember being pretty impressed that they did in here
after ah went pay i didn't have the money to subscribe (being a lowly high school senior) so i dropped my account and then came back for a two week trial when the GVs were introduced. those were wicked cool and at the time i tried real hard to get my friends to play the game with me.
when i subscribed in fall of 2000, 1.04 was incredible fun and then of course the AK scenario which really dragged me in. I dont think i would have kept with the game if it wasn't for that scenario because i had such a good time panzerdriving with dinger. right after that i begged hb to let me be one of his cronies and he said yes and then it was all downhill from there
it seems like every new release we get some cool new feature that really adds to the game.