I was playing around some more with the gl on the swamp map last night and found, if conserving ammo is not a consideration, it's pretty effective at carpet-bombing an area where you can hear / glimpse specials prowling around in the distance. A few near-misses will usually take them out well before they can even begin a charge. The thing about being mobbed while reloading the shotgun is that it's great for 'shoving' -- which is really clubbing, and frequently killing them with the butt. So I stand by the shotgun as the best all-round weapon except perhaps in expert modes which I haven't tried. Also haven't tried the ak yet.
Yeah the shotgun is great on normal and decent on advanced. It's no better at pushing than any other weapon though, that's all the same.
And yeah, another thing worth mentioning with shotguns is that they're amazing against the tank *if* you insert the muzzle into the tank such that all of the pellets are hurting him :Y
Also, what's your Steam name? I don't believe I have you added.
I did buy L4D2 the other week. I need to install it, and clear my desk.