I picked up a full set of the modern figs and the 2 WW2 figs shipping with them here just the other day... I'm overall pleased with what I got. I'll give some mini-reviews/thoughts on them here now...
-US Spec. Forces Afghanistan... The Special Forces guy with bare arms is pretty much lacking the things Ryan already mentioned, so you're right on with this one. The joints are not attractive and show green spots throughout instead of casting it in flesh tones... And no wrist articulation? That sucks, plain and simple. If you can see the elbow joints so much what's the big deal about gaps at wrist joints? Sleeveless arms are just gonna have to accept they're ugly with articulation and move on.
No working holster also sucks, and I'd add that a non-removable hat is inexcuseable really... Not perfect, but at the samet ime it's probably the best sculpted figure they've ever done... The realism on it's unmatched, and it shows how our special forces are fitting in over in Afghanistan... It's a brutal area, and our troops are adapting to it in weird ways.
-Night Stalker... One I don't even know wtf a nightstalker is. I've never heard the term, but I can only assume the guy's a chopper pilot... What he flies, I have no clue. Every chopper comes with a pilot so this guy's an enigma to me. He has a pilot helmet on though... Though why does he come with a big, I think, M-60 machine gun? I don't get it...
He does come with a cool laptop and GPS though and that's awesome to me. A great sculpt, but like the Afghan spec. ops guy he has no wrist joints and like you said Ryan it's REALLY inexcuseable on a figure who has gloves on. For christ's sake just give him the wrists from the other army figures since they're the same gloves... Oh and no working holster, again, when they have a goddamn working holster all ready to be used that they've put on figures to-date.

This sucks really and is a regression IMO.
-Sniper... I love this guy. I don't mind the goofy guille suit without the "back" on it. To me I'll only display him all guille'd out anyway.

I'm gonna cast the hat and suit for star wars uses too, it's fantastic. The figure has a very hard time holding his sniper rifle(s) though I've found, my only complaint about him.

I like that he comes with two rifles though... Again though, no working holster... WTF is the deal with BBI ditching working socom holsters?

-Navy SEAL... Best of the bunch is the Navy SEAL figure. He features diving vest, diving fins, camera (I think?), 9mm SMG, boonie hat, goggles... Stuff all fits the figure well though the breather doesn't fit to his mouth right, it's too low.

It'd be nice if the goggles/mask would wrap on the boonie hat too instead of only on the face. No huge deal there though...
Articulation's perfect really, though BBI could step it up by adding mid-thigh swivels to figures... And again no working socom holster and it's a must at this point. Screw making a new holster with a molded-in gun, just give us the old one you already ahve tooled up and we can put the new kick-ass pistols in it ya know?
Anyway, great figures...
The WW2's are better IMO for the most part than 21st's but I'm disappointed that their backpacks are basically stuck on them. If you take them off the web gearing looks like ****. The Army Ranger's helmet is too small too for his head, but no big deal there to me, I have tons of helmets available to slap on him.
Some more rifle-ish hands would be nice for posing the figure with M1-Garands but again it poses ok... Just takes some work.
Overall, great figures, and for $4.99 you can't beat this kind of value. Even the worst BBI figure rivals the best Hasbro figure... That's not a good thing for Hasbro, but it's great for a small company like BBI, no doubt.