As some who's owned both, the Touch actually does improve a great deal over the Voyager, but it's not something you'd notice unless you got some quality time in with it. On the surface, they seem pretty similar, but the Touch really trumps the Voyager big-time.
I did some research into Boost when I was thinking of dumping Verizon. They seem okay, but their coverage isn't great outside of major cities. Their phones (especially the Clutch) are decent yet very basic but can be made better if you mod them (replace the default web browser with Opera Mini and Boost's GPS Navigation for Life in Pocket, for example).
I started a thread about them here if that helps.

