I use sketchup all the time and think it's brilliant. There is the argument that I spend as much time building stuff as I would just drawing it all out repeatedly- but I actually quite enjoy doing it as well- and I get to reuse a lot of props and sets again as they're so easy to switch around into something new.
I've made several half hearted attempts at a Lawmaster, but I've never persevered- mainly because I think I've tried to stray away from the classic version a bit too far and they've ended up looking a bit rubbish instead. I think Kev's really nailed it though.