I've got Somalia, and I like it a lot. The classes and rules are well-done, and the background and campaign resources are very good. There's even a whole slew of "social feats" specifically for an all-military campaign, so that the soldiers can do something other than shoot things.
There's also two adventures and a campaign framework, plus ideas for adapting the sourcebook to other settings like near-future, etc.
I've been meaning to pick up Colombia, but I haven't found it yet. I'm not sure if I'll get Afghanistan or not, since it isn't D20 Modern.