What started it all for squad level infantry combat was not ASL, but Squad Leader instead. Squad Leader was later expanded by several supplements such as Cross of Iron, GI Anvil of Victory and Crescendo of Doom. Each expansion took the system further away from the basic principles and pushed the system towards ASL in complexity. When ASL expanded towards Starter Kits, it was reverse development to what Squad Leader experienced.
The reason for acquiring Squad Leader was two-fold. Friend had ASL, which I did play before SL, and some of the basic maps are essential for ASL. I was so new to the whole ASL thing that I actually liked Squad Leader, and very soon played through every scenario in the game. Cost of ASL was then just beyond me.
However, it did not last. I did soon (about the time I got Cross of Iron and Crescendo of Doom) found that the system was about to outlive it’s own principles for fluency and simplicity. Every expansion added layer upon layer to the base system. Additionally to new revised counters that reminded me more and more about ASL, there were many, many rules exceptions that created hydra which was becoming more of a monster than ASL would ever be.
Sad, but SL design principle failed miserably. It moved ceaselessly towards unmanageable complications. Only realistic way out was to rewrite the whole and incorporate the brilliant ideas in unified system. That would then be ASL – system where everything was in order, and standard. For SL it was a huge leap in two ways. First it pushed the idea of SL into oblivion (manageable, easy to learn and fluent squad level system), and added barrier of seemingly overwhelming complexity (illusion really, if thinking the extensions of SL at this point). However, it is not fair to say that ASL is the root of all evil, because SL was the start of the transformation leading to the only logical conclusion.
So, I have strong opinion about SL. It was excellent game as long as it was kept without the expansions. SL was playable, almost like the ASL starter kit. Fun and fluent. After first expansion was published ,the downhill started. By the second it was already so steep that it pulled the good parts of the base game with it. I ended up keeping the maps but sold out everything else in favor of ASL and have never regretted.
That said, extensions were not ill conceived. Cross of Iron was probably the only one that was acceptable as far as rules changes were concerned. It introduced many new aspects to the game, but at least there was attempt to keep the whole together. Later ones started to rewrite the very basics of the system, such as the counters. All the expansions had solid footing if considering the modularity aspect. It is just the execution that did not live up to the standard. SL scenarios are worth converting to ASL because it is the best way to experience the SL content.
Still, after all the years, SL alone is excellent game, even today. It can compete quite fair and square against other squad level games and provide hours of entertainment. Some of the ideas that SL introduced at the time were revolutionary, and some of the best concepts are still alive and well today. That stands a witness to the quality of thinking around the base system.