Name another simulation that lets you fly around over Vietnam in a Huey gunship with any semblance of realism.
Vietnam MedEvac. Sure you can't shoot rockets in it, and there are little soldiers who scream like maniacs everytime you fly overhead. But a lot better choice, IMHO, if you can find a copy. I think Beach wrote a review about it if you want to know more.
About Whirwind over Vietnam..sometimes, my friend, there's something that's not even worthy of your 5 bucks. This one is a good example. Well, IMHO, of course, but it seem like there are many who share that thought.