As jmfowler touched on with the IES issue, will this service support 3rd party plugins, ie deformation plugins for Lightwave?
I've had issues with Rebus as well. I'm sure a fully automated render farm works well (when it is working well ) but ended up using Farm render as they have someone looking after your renders.
Regarding some of the flat reactions to this service, the demo was a bit odd.... talking it up about the PI tiger then go on to demo hard surfaced transformers. Chalk and cheese.