As a computer scientist - I follow the 'kiss' principle: "Keep it simple stupid."

There WILL be a problem - sometime. I don't know the life of the system. I'd be surprised if it's more than 15 years.

Has anyone had any experience with Grohe Allure F-Digital yet? We're looking for a thermostatic system my granddaughter, who has a disability, will be able to operate safely with minimal supervision but I don't want to spend big bucks on an unreliable system.

We have found that digital shower controls are largely unnecessary. Turning a handle is a very easy operation and trying to push buttons or utilize touch screens with wet hands is not a great experience. If you are interested in a digital shower control you might want to consider Delta Temp2O. Delta's temp2o shower fixtures have a digital display which tells you the temperature of the water. It also represents the temperature in colors with a small LED light. Blue for cold, magenta for warm, and red for hot. We wrote an article explaining some advantages of these Delta temp2O fixtures which has a few videos and customer reviews. I think having a digital element in the shower can be very useful, but to turn the water on and off, I'd stick with a handle. Here's a link to the article if anyone is interested: Delta Temp2O Shower Faucet Controls