I've played the course, but my game is pathetic so not very instructive to most people here. I live only about 30 minutes away, and I've been there for one reason or another several times.
Most people like the course, but I'm not crazy about it. I object to forced carries over water on the approach shots on the first two holes, and way too much water on the last four as well. But that's just me, as cited above, the pros apparently love it. It has large greens, and is an excellent spectators course, real stadium design. There is one excellent par five on the back ninie, the 14th I think.
It is a remarkable feat of engineering on a flat site. The Peugeot Golf Guide lists the Frenchman Hubert Chesneau as the architect, with Van Hagge as consultant. Considering that Chesneau doesn't have his name on any other golf course, I would surmise that any merit to the design comes from Van Hagge.
Golf National is an adequate, if not brilliant venue for the Ryder Cup. It's a solid design for the pros, with no obvious weakness, forgiving the overbearing clubhouse behind the 18th green. It has several important advantages apart from the course itself: close to Paris with all those fabulous hotels and restaurants, within an hour of both Charles de Gaulle and Orly airports, easy access on wide roads, abundant outdoor and indoor space on site, plus they've been holding the Fench Open for many years, one of the bigger money European Tour events, and so they have acquired tournament preparation skills and equipment.