At the same time I have my limits as well... If the set turned out to be nothing but made up clone repaints the rest of the way through, like an orange #33 Commander repaint, etc., etc.
Well, it's not going to be all any one kind of figure from here on out-- so it's not going to be all Clones, and it's not going to be any Clone Commanders.
Who, exactly, is writing the back story to this set and the characters (names, jobs, etc.) involved in it? I'm curious about that... Is it Hasbro? Is Lucasfilm feeding the "story"? I'm a little perplexed on all that jazz.
To tell you the truth, I'm not exactly sure. Lucasfilm always has final say on the names and packaging copy, and they aren't shy about making sure things align with their vision of the characters or events. They even renamed a few astromechs here and there. While I don't know specifically who wrote the bio information, I can tell you it wasn't me.

I think not super-articulating the clone commadoes has been the worst idea since the "no-neck" Maguilicutty rebel fleet trooper.
Adam, how finished are these sets? Is there any chance for some last minute retooling?
It's my understanding to meet the ship date, they're pretty much finished-- but the images you're seeing (and that I've seen) aren't final product, which means minor things like necks, holsters, paint, eyebrows, all that stuff could end up looking slightly different on the final product. Given the costs needed to make a new tool for new legs, that's something that isn't really doable at this stage. (I'd prefer to have knees too, but such is life.)
Could some of these Mando's be coming from the Clone Wars cartoon coming out? We've seen very little, and it being more then a 5 minute cartoon there's probably a lot of ground to cover for the cartoon to delve into. Somebody after all has to keep training the newbies on Kamino. Alpha on the poster has the "eye" markings on his helmet much like the #41 clones that are coming with the set. I plan on buying the set regardless, just hoping Hasbro/EE aren't pulling these characters out of there 
If any of these figures appear on the TV show, well, I'm not privy to that-- I've seen and know as much about the show as anybody else.
You'll recognize a few of the figures from existing projects you may have seen. If you read the novels, you might recognize Omega Squad (well, from the text, I guess.) If you read the Star Wars Insider, you may recognize Rav Bralor's armor as looking a lot like [http://starwars.wikia.com/wiki/The_Mandalorians:_People_and_Culture]a picture from one of their Mandalorian articles[/url], and there are going to be a couple of things in the set like that. And a couple, like Llats Ward and the white Clones, that are more or less new.
There's a pretty big gap between Galactic Marines and Airborne Troopers and dyed black or logo-stamped repaints of things that were never in movies.
*shrugs* There's also a pretty big gap between Galactic Marines and the Kashyyyk Trooper and what appeared in the movies, too. I still wish I could've got a few more of the bugger, though.
Also, black repaints are kinda popular with collectors-- at least in Japanese toys-- and these ones have the benefit from having appeared in a few EU sources so far. But if you're not a fan of the EU, I don't blame you for not thinking much of a black repaint.