One of the first platoons I painted up for my US Riflemen was the Weapons platoon, because I figured every US force needed this kind of thing. Turns out I was fooling myself. I used it for two games and it didn't do anything at all, really.
The platoon is divided up into two sections: light machine guns and light mortars. You always get three 60mm mortars, which could be useful in a direct fire mode or to pin the enemy, but if you have other artillery, you're better off using that as the 60mm has a lousy fire power rating. When it comes to the LMGs, you get 1 section (two teams) for the standard 85 point platoon, and can expand this to 2 sections (four teams) for an additional 35 points, making the full platoon (minus Jeep) come in at 130 points. This is way too much, in my opinion. The mortars aren't good enough to warrant the price, and the LMGs are all but useless, unless you're playing against an infantry horde who's about to assault you. You get ROF 5 FP 6, which is fairly ok, but the range of 40cm makes the LMGs rank in among the worst in the game for infantry MGs.
I have been meaning to put the platoon in again, attaching the LMGs to my rifle platoons and keeping the mortars in a platoon of their own, but I always find I have a better use for 130 points. For larger games I tend to go with a machine gun platoon, giving you ROF 6 range 60cm weapons that you can attach out, and a mortar platoon giving you the much more useful 81mm mortars (which are capable of firing smoke).
I don't know if I'm "doing it wrong", but I just find the weapons platoon to be next to useless. I would appreciate being called dumb and shown how to use them by any veteran US players out there.