I don't see much discussion here regarding UPB. On cocoon tech.com, there seems to be several folks who like it and have used it for a long time. I have not heard of such long delays with UPB. I doubt it would still be around if this were normal.
I would not go back to X-10. I would definitely use UPB before X-10. But...I started having trouble with X-10. If you don't, go for it.