I know David, and we've been there many many times over the years. My OH is an engineer in major constructions, and we regularly visit the Tarn/Millau areas, so we've watched the progress of the bridge from 'conception'. We actually had bets, years ago, on where the route would actually go across the valley - and needless to say he won (being only metres out of the actual point where it crossed! We used to go to the visitor centre every time we went down there.
When the viaduct was opened in December 2004 we were in France for the opening day, but we weren't the first British across, unfortunately. We'd made a special trip to see it and to be at the opening ceremony, but they actually opened it a day early. However, that day it was only open to local traffic and people with 'permits'. Had we realised that the first 'public' crossings would not take place until the following day we'd have made more of an effort to get there early that day!
Since then we've driven across it several times, but now prefer to go back down into Millau via the old road, and marvel at it from underneath or one of the other viewing points, rather than drive across.