I have the boxed version. I had to stop playing after about 4-5 levels, due to RL commitments, but I roughly have an idea on how difficult the game is overall. If anyone has questions about it, feel free to ask.
Yes the game is very difficult. You will need to pause the game a lot, if you want to minimize the number of tries per level. No unit is useless; you will have to learn how to maximize the use of each unit, as well as its alternate fire mode. It's very much a tactical game, and you'll spend more time concentrating on troop management and placement, rather than resource management. Of course, there's only one resource to speak of, so that also accounts for GCII's gameplay.
For those who don't know, in GCII, you get resources by controlling checkpoints. Lose a checkpoint, and you lose funding. Think of it as Battlefield 1942's Conquest game mode, in an RTS.

I think it has 4 bonus maps and it makes it Special Edition.
http://www.fileshack.com/browse.x/2584

I, too, was wondering what made it a Special Edition. So, I searched on Google and MobyGames lists a Special Edition of it and it says "This Special Edition of Ground Control II: Operation Exodus includes a making-of DVD with developer interviews and other extras like artwork and trailers.", which seems to match up with the fact GOG's version also has a making of video and artwork.

Awesome. I remember playing through the first campaign some years ago, which was pretty cool. The second campaign was impossible at the time though.

Fantastic thank you Gog another great game to play. The partnership with Rebellion means we are getting some really great classics to play again.

Wow... What a nice surprise on this stupid day.
Played this back in the days, a great game. :) I recommend getting it, if you like RTS games. This should not be missed by anybody. :)

i played the demo ages ago... i think ill'grab this one some day.
added to wishlist :]
..and as someone mentioned above - please, pleaaaaaaaaaase give us AVP now :)

After the recent fiasco with the racing games, it wouldn't surprise me if GoG have become super-cautious about games based on licenses

Does it have in-game saving? or did they resort to "longevity by repetition" like they did with the last one?
I simply can't afford to not exit the game whenever I want. I have a life and sometimes it calls when I least want it to.

You can save in game whereever you want.

You can save wherever you want.. but it's not as good as the original game. sigh. why are things never perfect???

Link to the first game is busted:
http://www.gog.local/en/gamecard/ground_control_expansion
vs.
http://www.gog.com/en/gamecard/ground_control_expansion

Sweet deal! I may just have to grab this one.
Do we really want another licensing hassle? It's not like the license is purely in Rebellion's hands. Or even Sega's. It's a great game though. One of my favourites. A GOG that never will be.

I'll have to help burst your bubble too Emre, sorry.
SEGA has the license for the Alien properties, Rebellion made the old one and is working on a new one, published by SEGA.
I hope we're wrong but as far as I've read that's the case.
It might be fun to see some of Sega's(ok I'll stop capitalizing) PC games on here.
Flesh Feast and Vigilance come to mind.

So, there, I bought both just because they're so cheap, even though I already have retail copies of the first game and its expansion.