The Flames of War Vietnam book is Tropic Lightning. Tropic Thunder is the Vietnam movie spoof with Ben Stiller, Robert Downey Jr. and Jack Black.
I haven't played it, but I've got the book and there are some cool scenarios in it. It looks like it would work nicely for the bigger battles that the rules are meant for (Ia Drang and the like), but probably wouldn't work as well for more guerrilla-type stuff, unless you cooked up some house rules.
As long as your fine with sticking more to the bigger battles (which admittedly, didn't happen that often), I think it would be a fun game. The helicopter models are quite nice too, and I really like the Sheridans as well.