I had ASL for years and it sat gathering dust on my game shelf. Never got past the first couple of scenarios. Never got into tanks or guns, just played infantry scenarios occationaly. Then a couple of years ago I decided I was tired of looking at it sitting there doing nothing so I got out Jim Stahlers Programmed Instruction Guide and buckled down to learn it. Learned how to move and fire Tanks, learned AT Guns, even tried to figure out the Off Board Artillery rules (IMHO the hardest part of the game). Anyway about the time I had a partial grasp of the game, along came CMBO and I haven't picked it up since.
But having said that, I really did like ASL. I love rolling the dice and the feeling of, "All I need to do is roll 8 or less and this tanks history!" type of thing. The anticipation of the tumbling dice is something that is missing in computer games. I'll never forget debating with myself as I was facing down the front hull of a Panther tank with a bazooka, whether or not I should try to disable the beast with a deliberate immobilization or fire away and hope for a turret hit (I was facing the side of the turret). Deciding to go for broke I went for the turret and jumped for joy when I rolled them bones and they came up "snake eyes", a critical hit! I could almost see that Panther going up in flames! Like CMBO, I have a lot of fond memories of ASL.
I guess to answer your question, buy if you can afford it....but I would recommend Jim Stahlers Programmed Instruction guide to learning the game. It takes some work, but it makes learning the game easier. From a purely gaming point of view, ASL like CMBO really is a great game.