Hi,
What you have brought up is an interesting question because I also have noticed mention of the A02 and H02 being obsolete. What a revelation since I have been playing the H02 for years with great results. My opinion is that if you can keep the A02 with aces without mistakes and it is comfortable for you then this is the count you need to play. I mean, why waste your talent? Now, a couple of comments about the Zen which seems to be the system of choice at least for this message board. The Zen is a damn good count! That being said it is not the A02 and will not perform like it. I believe the main reason the A02 isn't getting the respect from this board is that most people aren't able to play it comfortably and correctly. So, maybe it is not the count for most people but that doesn't mean you should tell someone who can play it flawlessly for hours at a time they should play the Zen. That just doesn't make sense. Sure, you can argue that the Zen is easier and would produce less mistakes but remember I am talking about someone who can play the A02 flawlessly and make it look easy. These people do exist! I do have a lot of respect for the Zen especially at single deck with the dealer hitting soft 17. It seems to excel at this game, but still underperforming the A02, H02. With the rules changed for S17 it falls back a bit. Of course, then you can argue that if you already have the ace on the side why not use it for playing also. Then, the A02, H02 pull away in any game. Yes, it is a bitch to keep the ace in shoes but it can be done and with time effortlessly.
BTW, I would not recommend the Zen for someone starting out because there is an easier system. So, for all those Zen lovers who argue for simplicity giving this reason that the ace sided counts are obsolete here is my answer.... Play the TKO. It is every bit as strong as the Zen and it is a 1-level count. Yeah, you have to deal with negative starting counts but it is still easier than keeping a 2-level count and you can use the running count in single deck for betting without losing any efficiency.
Good luck.
Beast