As a player, I wish my DM would make almost all of my rolls for me. For all of the reasons stated above, there is no way to avoid meta-gaming (unless the *group* is really darn good--note the word "group," not "player"--it really is a group dynamic, as seen above) if the players get to make all/most/some of the rolls. I think my DM doesn't do it because he also rolls the dice manually. Having a page of d20 rolls generated by a program (AOL chat rooms have this function, and anyone can download AIM for free) or even just done up in spare time makes so much more sense, and it doesn't alert the players to the fact that a roll has been made. I think my current group is, for the most part, good enough to not question what a random roll by the DM is, and some times he rolls a bunch of dice for no reason at all (major scare factor when used sparingly), but I think it's better to have a sheet of pre-rolled numbers and cross them off as you go. I wish my DM would let *us* do that, but I've asked and he refuses.
Speaking of which . . . do any of you (DM's) allow pre-rolled numbers? It would speed things up so much. Have a sheet of 20's, and then various amounts of the other dice based on how often they're used. Especially during combat, when a lot of time is spent figuring out what the action is, not to mention rolling several attacks, or whatnot. It bogs.