Clear Sky has some fucked up balance issues, all related to the fact that faction groups will respawn almost instantly as soon as they're outside of the active NPC range, so you can't permanently take a base: You can raid it, kill everyone, even get the quest reward from a rival faction for killing 'em all, but you won't even make it back to the rival faction's base before you'll see a message pop up saying that the other HQ was retaken.
Also this annoying fucking ass machinegunner in Cordon that respawns the same way and has perfect vision.
There's a Clear Sky Complete mod, but I don't know what its features are.
Other than that stuff though, I enjoyed Clear Sky. The new areas and different takes on old areas is cool. For some reason while it revisits most of Shoc's areas, they leave out some of the best, like Wild Territory and the Bar. The two big new areas, the swamps and the city past the Red Forest for the endgame are both really neat though.