Hi RaphaŽl, thanks for letting me know. My french is a little rusty, but it certainly looks OK from google translate.
I agree, using the inverse of the sexy move, and a perhaps a few more shortcuts can definitely speed it up. I kept this out of the tutorial because I think its nice to let beginners discover these tricks on their own. The tutorial gives them the bear minimum they need to solve the cube. Everything else comes from thoughtfulness and creativity :-)
PS: In case you haven't seen it already - a discussion on the method is here:
I'm a great fan of your site cube.crider.co.uk.
I'm especially interested in begginer method using only the sexy move such as your begginer tutorial. I wrote one myself (it's LBL, the first two layers are here : http://forum.francocube.com/topic6091.html) which allows symmetries and inversions of the sequence RUR'U' for more regular speed results.
I recently translated your begginer tutorial into french (http://forum.francocube.com/post154872.html#p154872)
RaphaŽl Cauderlier, french cuber