I must admit that I find myself rebelling wholeheartedly at the idea of the fresh-faced (nigh, pretty) and California-teenager-voiced Logan Lerman as D'Artagnan.
Were there no rougher-looking, British-sounding teenagers available in Britain? I know they are there. Go to any soccer match. Grab a random lad from the crowd. Cast him as D'Artagnan. You're good to go.
Or even real French people. Sometimes French characters are played by actual French people. The Musketeers of the Guard were French. The real D'Artagnan and the fictional D'Artagnan were also French. So I would be okay with a French teenager, even a too-pretty-to-be-D'Artagnan one, if he had a few convincing fake scars on his face and did not sound Californian. :)
And the trailer has the whole movie looking a bit long on special effects and cleavage (always the temptation with 3-D, I think), and short on actual acting.
However! The California teenager voice is wholly cancelled out by the dulcet tones of the trailer's brilliant narrator, whoever he may be. I find I have absolutely no problem with the trailer's brilliant narrator. Nope.
As for Athos, il est parfaitement parfait: un mousquetaire très beau et charmant, avec la voix la plus merveilleuse du monde, et la meilleure expression du visage jamais vu dans une salle de cinéma partout. Et vraiment les plus beaux yeux. Les plus beaux yeux.