I have all 3. I picked them up for under $250 each over the course of the last year. For that price I think they are worth it. I don't have a respectable preamp as of yet, but once my M4 arrives I'll be running it W/D through a Rivera TBR5 and my Sunn 4x12. The plan is to get it dialed in and then my other guitarist wants to have a Youtube shootout. He has a friggin mothership rack using a GCX for pedals and a Gmajor through a Mesa Rec Pre and 2:100. I'll be sure to post something here when I do.
The units color your tone a bunch. I'm thinking W/D will balance it out though. If you're looking for something really easy to dial in that will work in a live situation and can get each for under $250 I would say do it. On the flipside consider you can get a Gmajor or Mx300 for less than $500.