I know this has been discussed already but the palms need to face down really especially if its going to rigging.

Though the T Pose with arms at 90 degrees is pretty much the norm for rigging, Im finding having the arms bent is getting more and more common. It does actually make sense to do it this way as the armpit area can be skinned easier without worrying about geometry disappearing and doing strange stuff when its out of site. Also the geometry is more 'relaxed' when modelled this way too and looks more natural in the bend. Also it deforms better when raising the arm too IMO.

Modelling a twist in the forearm does give the advantage of a better looking deformation as well, though there is ascript or two out the to stop it collapsing at the kinning stage if it is done without the twist being built in. Its basically a cluster script called a DQ if Im correct and is available over at Highend 3d

cheers
Jay