Man I love them. Davich, Sagisu, Dragonauthor and I played one this weekend. We didn't finish, but it was pretty fun. Sorry, I didn't take any pictures :(. I definitely need to refine it, but it was bearable.
I combined a couple rules I found on dakka dakka, I sort of forget who they were from though, sorry. I really need to get better at this :P. Pretty much what we did was make a map and take tiles and had battles. Expect for tyranids we all had a reserve of 4000 points that we drew up before hand. Our guys could die and gain experience. For each battle each person rolled a dice and multiplied the results by 250 and that was how many points we could use.
Tyranids however started with 1000 points and got more for the points they destroyed minus the points they lost each battle. Ha ha one battle I had 500 points of scouts terminators, Cato Sicarius and a predator take out 300 points of hard hitting tyranids before escaping off the board so he couldn't get us.
All in all, it was fun. And everyone should play campaigns when they have a free weekend.
I found the posts I got the ideas from