I use the Raspberry Pi version 1.0 of the board (I think they’re on 2.0 now) and it works fine. I don’t believe there’s an RTC on it but I set it up to use NTP and it works fine. With the Raspberry Pi one, I have been able to upgrade OpenSprinkler via the web interface.
Just put it in use about a month ago but so far no complaints, everything has worked great.
FYI, their products seem cheaper if you order them direct: http://www.diygadget.com/lawn-sprinkler-controller-and-accessories.html
The one you linked to is a little different but thus far mine has been fine. I have 10 zones which is why that option was attractive to me.