I have both the SIEGE engine original and the 5e variant (which is a standalone product using the 5e rules instead of SIEGE), and ran an AA campaign using the 5e version. Actually, we really enjoyed it, and I think very highly of it as a system for pulp-ish gaming in the late nineteenth thru the traditional 1920s-1930s era; you could likely use it for more modern campaigns than that.
It hits the sweet spot of a class-based, progressive power rpg system while having genre flavor. I would recommend it most highly for gamer groups familiar with and most comfortable with such systems; more open, diverse player groups might enjoy CoC or other systems with different mechanics.
I should add that I have a collection of nearly every pulp rpg ever published—well over 30 at last count. AA is among my favorites for its ease of use. So much of pulp gaming is in the details of the setting and the scenarios anyway, not necessarily gimmicky mechanics. We are about to start another Supers- based pulp game, based in part on the cult movie “J-Men Forever” and for that we are using HERO/Champions because of the Supers builds/powers issue. But if I ran another pulp campaign, AA would be one of the three finalists with GURPS and Call of Cthulhu as the others.
