The train journey over Dovre would be considered spectacular, if it hadn't had the Bergen line for competition! The mountain crossing is nearly as high, and just as bleak, but it is shorter. Most of the journey is throgh quite nice valleys, up to Oppdal and down fra Dombås, where the mountain section starts/ ends. Of course, if you hadn't already booked your tickets, I would have recommended a detour down Raumabanen, the branch line to Åndalsnes from Dombås (connecting trains to most Trondheim-Oslo-trains),

Lillehammer is a nice stop-over, and with hourly trains to OSL staying there is convenient for departing the next day.