I saved Gangbusters for last because I have a little bit of hesitation regarding getting into it. Boot Hill I'm already on the road to owning, since I now have a gratis copy thanks to my friend Pat. Gamma World ought to play easily as sci-fantasy D&D, the Mutants & Magic angle also opens up the possibility of a Thundarr the Barbarian type scenario. Dawn Patrol is just a single boxed set and that's it.
But Gangbusters leaves me a bit indecisive. First off, I once owned a copy and long ago sold it. I've already bought back too much of my childhood as it is. Second, it uses a system of classes, levels and xp's. I'm not one of those rabid anti-class-and-levels people. I'm running Heroes Unlimited right now, for gosh sakes. I just worry about getting into a level and xp system because they are invariably designed for long-term play, and I don't run long-term games anymore. For my last two class-and-level campaigns we simply advance a level between each session. Which might be the solution to that particular issue in this case as well. Third, and perhaps most importantly, I find modern games are tough for me to run. Call of Cthulhu is hard and Gangbusters is like CoC without being able to fall back on magical deii ex machina.
Still, the reference works seem to like this game. Swan calls it Gangbusters "an overlooked gem, a minor classic". Schick calls the rules "well-done, underrated". Swan recommends the adventure GB5 Death in Spades, which looks like an oddball mystery scenario. "[P]lot elements vary depending on what the GM draws from a deck of playing cards" according to Schick. Could be hokey, or it could be great. GB1 Trouble Brewing is an intro scenario describing Lakefront City (a cheesy Chicago knockoff) in more detail. And GB1 was written by my main man Tom Moldvay! GB2 through 4 look decent too.
What's nice is that some of these products are starting to appear as downloadables.