I was planning on going the Insteon route but I've been reconsidering that lately. I have four or five 3way or 4way circuits in my house and a grand total of 72 switches so any route is going to be rather costly, but it looks like some upb slave switches are as low as $23 so that's going to help out a lot.
i just got done putting about the same number of upb switches in my house. started using some of the cheaper sai usr switches. ripped them out after about a week. they don't have the functionality of an 1140 or 240. probably my biggest issues was the inability to program the LEDs on the usr's to mimic what the 1140s 240s were doing. but hey, maybe i'm too obsessed with how they looked.