I'm getting involved with a new gaming group, and they're new to Arkham Horror. I stripped out all of the expansions, and we played with only the base game.
Got Abthoth as the GOO. Had three gates open (The Witch House, The Woods and Unvisited Isle) then monster surge after monster surge after monster surge. The game went really long as we were light on clue tokens, and the huge volume of monsters forced the terror track to advance quickly, depriving us of quality weapons and items. The Southside Strangler hit and killed off a few allies... but we were never once in danger of losing. When we finally sealed the 6th gate, the GOO had only just filled over half of the doom track. The game took almost four hours to complete (new player, but mostly a large portion of do-nothing type of turns...) I find I really miss Dunwich and The King in Yellow. Man, it's hard to go back to the base game!