The GertBoard does not have to be "powered" by the 8 bit AVR processor. Any of the other digital circuits on the board can be directly connected to the Raspberry Pi through the 26 pin I/O connector by using GPIO or SPI.
Raspberry is a great success story. I am sure we will see many new interfaces/upgrades to this useful device. Many students/developers have ordered these kits and have already started developing applications.
It's an amazing product which can cater to numerous segments like hobbyists, education and small commercial startups which even they didn't think of. It just goes to show how a simple and efficient design can address multiple needs.
This is one nifty board with lot of software support for anyone to dabble in.
I like the PiFace design because it adheres/is compliant to/with the physical shape of the R Pi Motherboard.
The preceding I/O GERT PCB did not and thereby reduced it's utility for professional use with consideration to 'packaging'.
Another factor that has hopefully been eliminated are the physical variances, and connector locations, between the various versions. Maybe I've been working with MILspec too long, but it sure is nice to have the board dimensions and connector definitions stabilised!
A point of momentum seems to have been reached whereby inertia will carry it forward.
Here in VietNam a USD$35 hits the USD$100 mark, about one-third of most families incomes in Ho Chi Minh City, by the time it has been sourced and shipped from Singapore and our national government has imposed it's duties and VAT!
Notwithstanding these impediments, there is a fledgling User Group, with a bilingual chatroom and great enthusiasm building.