I don't know if I agree with the all glass, just from the stories I heard I would believe that all the information given would stop the student from looking outside.
Considering how many new planes, especially the larger commercial planes, have glass panels now, I think it's a very good idea to give students at least some time in one. Friend of mine tried to get his IFR rating this summer, he was ready for the checkride when the plane broke down. The only other plane available had an IFR GPS system, one of the newer all-in-on packages with all your NAV/Comm in one box. After 3 hours in it with the instructor he gave up for the summer, was just to complex to learn in a short time. Granted he openly addmitted it'd be easier than the older systems once he got it figured out. So, I think it's definitly a good idea to give students, or new pilots some time with a glass panel.
Personally, my only grip is that the little buttons on most systems are hard to use with gloves on, or in turbulance. I like my big old knobs and dials.
Phil