Eh, Retribution at least removed that god awful games for windows live. But the main campaign was just copy pasted and changed only a little for all the races. It might be fun, but I personally like the more focused original more.
Still, the last stand mode is fun, the multiplayer isn't bad, and there's some nice moments in the campaign. But I felt the campaign was mostly ruined by making it so easy to just buy units. That 'band of brothers' feeling was lost by simply making it a steamrolling excersise, were defeat simply means walking back a bit and waiting for your army to fill up again.
As you said, best to get it on sale.
It IS better than chaos rising though, I would say. And it certainly gives you more content for your buck.