In reply to AlanLittle:
Hi Alan
We did this last year, driving from Ailefroide to do Visite Obligatoire. It's a nice drive - around 2-3 hours depending on the traffic (which can be fairly slow over the Col de Lautaret - clogged up with caravans etc). We set off late morning, had lunch in La Grave on the way (great place to stock up on supplies for climbing the next day), then walked in to the Soreiller hut in the afternoon/early evening.
We used the Oisans Ouest guidebook, but there are also other books available (some in English) in the shops in La Grave.
I've done 3 routes on the Dibona and I'd say that if you're going to do just one, make it Visite Obligatoire. Every pitch is absolutely stunning. Bolted, but very sparsely on some pitches and a few tricky moves. I carried a few cams and they were useful in a couple of places. I thought overall it was quite tricky for the given French grade (6a+ I think), but the hard bits are all very well protected. Some great exposure, especially on the pitches after the Boell Ledge. The pitch immediately after the ledge is awesome - steep jug pulling on perfect granite. Due to the fairly sparse bolting route finding can be tricky in places. I can still remember where it would be easy to go wrong, so if you need any info drop me an e-mail through here and I'll see if I can add any useful info to the guidebook description.
The Madier route is also good, but a bit of a ramble in comparison. We did the crux crack, which was nowhere near as bad as most people would have you believe. Good gear in the back of the crack and face holds to help if, like me, you're not much good at crack climbing. The crux crack was the highlight of the route for me.
Another good option is the Soreiller route (around E1) - less fixed gear, although there are bolts where it really matters. Great climbing all the way, but take a rack.
As others have said, whatever route you do will be memorable, as it's such a beautiful mountain. Enjoy.