Not bad once you get into it, but you have to complete lots of training missions before you can play online, which gets really tedious - its like sitting through your IDT's with a moronic yank talking non-stop.
If you want a quick fix couter-strike source is a better if more unrealistic bet. Other games worth a look are battlefield 2 if your PC has the HP and Swat 4 if you prefere a slower pace that doesn't always involve just killing everyone.
My favorites though are Call of Duty 2 and Brothers in Arms.
I'vfe just bought a new X Box 360 and have glued myself to the control pad, not only for Battlefield 2 but also for Ghost Recon: Advanced War Fighter.
Absolutely cracking piece of software. It made me put on my war face.
Americas Army basic missions that you have to pass before getting online dont actually take that long. The last one (The Killing House I think) took me a bit of getting the hang of, but wasn't too bad.
Once online though it takes a while getting experience to be able to go onto bigger maps and alot of servers wont let you on without a certain level of experience (fair enough, stops their game being wasted).
Personally my favourite is Counterstrike Source (duh!). Much quicker to get into and easy to setup your own server.
For the Â£25 I paid for the game, I've had at least 500 hours of free play on it.
Still, as AA is a free download, why not just try it first?
Sadly I am having to revise that figure due to the incompetency of my university's IT dept. Just lost a whole hours worth of work despite it being saved!!! Worst bit is that the work I have lost was sheer genius top of the head thought which I now can't remember as all I want to do is go a insert my **** produce into the nose of whichever wise arrse that decided to scrap the use of the common floppy disc which every man jack is familer with and is universal with fooking usb drives which sod all people have or know how to use but because they thought "we have to have the latest hardware despite the fact that nobody else such as the students will actually be able to use it!!!!!!!"
right 'rant off' otherwise I will get bogged down in my desire to hurt certain people which fun as it may be won't get my work done
edit - finally caught up again albeit not quite the same now