Has anyone here used Sketchup for semi-accurate modelling?

I ask because I've been giving it a whirl so as to get a better idea of
what my options are for a house extension, and I'm very pleasantly
surprised at how easy it is to bung in things like toilets and doors
and stuff all to scale, and even get an idea of where sunlight's going
to fall throughout the year.

Not having used any other 3D software though, I've got nothing to
compare it to, but am curious if anyone else has used it in any way.

John

PS: For the uninitiated: http://sketchup.google.com/