Seamus,
The tool lid does seem a little thinner on the 5000/S5 Series, but they've been bulletproof so far. Here in the U.S., we did have a run of machines that had cordwinder problems and some issues with the elbow at the machine end of the hose. Those problems have been taken care of with this new series.
I've sold roughly 40 Mieles since I took them on last June, and the only problem that I've ever had is with a customer who uses hers daily in a daycare. One of the kids got ahold of the wand and busted off the release button, which was a simple and inexpensive part to replace.
Our local Molly Maids uses a variety of models to supplement their uprights. They usually clean five houses per day, and they have machines going on 10 years old.