Actually the extra missiles are a fire and forget. The first two DO lock on to a target and home in on whatever one it's selected. Problem with it is, if you see two people close-ISH to each other and can clearly target them separately with the viewfinder, they'll both end up going to the first locked on target rather than two separate ones.
And I've also noticed that the viewfinder control will get 'stuck' in some angles making it near impossible to correctly guide it through a small opening.