I started with SL in '82 (maybe '81?), really can't remember exactly, after an unusual introduction via a friend who described it much like an WWII RPG, I guess he thought I'd be more interested that way since we were D&D players. The bug bit me pretty good immediately, some time later we drove an hour to the nearest game shop and I bought SL. Another friend then bought each of the gamettes when they were available at the shop and we played the heck out of it including some very out of control DYO messes on 8 boards for giggles.
I was initially unhappy to have to buy the rules again with the release of ASL, but I came across a killer deal (1991 I think) where someone was apparently selling off all of their stuff due to moving, and I got the rules, BV, Para, Last Hurrah, Streets of Fire, and Red Barricades for $250 Cdn.
Absolutely the best bang for the buck of any purchase I have ever made, especially since it included Red Barricades.
I have always been a fan of a campaign regardless of the game, RPG, wargame, whatever, the big picture is the thing for me.
Scenarios are great for variety and particularly expanding your rules experience, but I don't think I'd be as enamoured with the game if there were no HASLs.
Early on in SL days we used the leader campaign rules, and I really enjoyed progressing through a SASL campaign.
Unfortunately I was really the only one in our group interested in long campaigns.
ASL will always be the masterpiece of games, detailed and absorbing while being many things to many people at the same time.