How does the SNCF Voyageur program work?

I'm planning some TGV trips soon, but despite being a member of two different Railteam frequent traveller programs already, from this question it doesn't look like I'd be able to credit the journeys on a TGV to either of them.

I think, if I want to get any credit for them, I'll need to join the SNCF Voyageur Program. The English language website for it has some broad details about the program, but doesn't really explain much about how you earn credit from TGV journeys, nor about redeeming them. It links through to various French language websites, but these all seem to have even less information on them, with all the important details apparently only available after you log in. (Since joining seems to take about a week, you can't just sign up and immediately see the details, grr....)

If someone with better google-fu than me, or someone who's a member who can log in to the site to get the full details, is able to post about the program that would be great. Specifically, I'm interested in:

• What tickets I can and can't get credit for
• What's the earnings rate (per segment, per mile, per euro, something else?)
• How do the different levels work?
• How do the rewards work?

Hopefully from that, I can work out if there's actually any point in me joining the program for just a few trips or not!