Obviously it's about the type. Someone piloting a big boeing that has the speed tape and limitations all woven into a neat little instrument, will have no use of a callout of the new speed. An an old thing like the SF340 requires some talking to get it right. The Vref's vary with the weight and there's no way of knowing all the speeds by heart. And the bugs don't bug them selves so we have to do it ourselves. PF is not going to look down and try to read the fineprint of the speedbooklet at that time so someone is going to have to tell him the speeds. And I think anyone will agree that it's good use of the PNF to do this whilst the PF is flying the plane.
Of course it's a good idea to keep callouts and such, as few as possible. But some of the callouts are absolutely vital. Basically anything to do with configuration. I know someone will bring up the GPWS (too low flap, too low gear), but I see these as the last wall of defense. The planes are individuals and they need to be treated as such. It's a very bad idea to fly an ATR the same way you fly an Airbus for example.
Regards/ LnS