What do you mean by "constantly"? Do you have a reference quantifying use?
My understanding is that modern military use of amphetamines is pretty much the same today as was figured out independently by both sides in WWII. Amphetamines are not useful for most soldiers doing most activities. They are mainly useful for pilots, because flight is boring and solitary. They are useful for sleep deprivation, but for most activities it's better to schedule sleep. They are useful for bombing raids, where you know how many hours out and back the pilot has to fly, and then can rest afterwards. Similarly, they are probably useful for commando raids, which are a lot more popular now.
If all pilots are on amphetamines when they are in the air, you might say that the military constantly uses amphetamines, but the individual pilots are not constantly using them, which is probably Eugine's point, and relevant to drethelin's question.
Since modafinil interferes much less with sleep, using it constantly may be a good idea, but I don't think militaries do.
Amphetamines are also used in ground forces; special forces are widely rumored to use them on many missions (with, of course, no official statements like we have confirming air force use).
(The HPMOR discussion thread after this one is here.)
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. There haven't been any chapters recently, but it looks like there are a bunch in the pipeline and the old thread is nearing 700 comments. The latest chapter as of 7th March 2012 is Ch. 77.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author's Notes.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight, nine.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: