It's a good standalone expansion, many hours of gameplay, loads of new items. You get to choose your own specialty with the character creator unlike JA2 where you had to choose a bunch of answers.
It's a pretty hard game in my opinon, even during night missions. Most of the opponents got night vision goggles,..some even got UV goggles so watch it.
All in all, I'd say, get this game. It's alot of fun and there is some replaybility even though it's short compared to JA2.