All in all I enjoyed RAAM's Shadow. I finished the SP yesterday, and if I had to guess I'd put this campaign at 2.5 - 3 hours total, or in other words half the length of the entire Gears 1 campaign.
I liked that it had anything remotely horror-based, or at least I got that feeling prodding through certain sections of the game. The schoolhouse could be creepy, and if played solo on Insane could probably be downright stressful. The RAAM sections were fun at first, but after the first trip as our resident superpowerful killing machine I lost my enthusiasm for his near-invincibility.
So I lost a little luster for it after my first playthrough, but I chalk a good bit of that to me not playing these sections in Arcade. Gears 3 has conditioned me to play the campaign for points in 4 player co-op. After I was done enjoying the environments and destruction, I was wondering what was missing. Points for killing grubs, of course. They don't particularly mean anything, but I've become accustomed to earning numbers for just about anything I do in a Gears SP campaign.
I wonder how I'll feel after playing Act II of Gears 1 again. I'm a sucker for those Kryll sections, haters be damned.