There are definitely wide-ranging opinions about the Meseta. My own is that the landscape did become monotonous and a bit boring after a while, but there are some fascinating places and churches along the way and so overall it was a memorable and worthwhile stretch.
A few of the places and things I enjoyed were: the ruins of the San Antón monastery (which someone posted a photo of above and which is also an albergue!), which was perhaps the most evocative place on the entire camino for me; the Puente Fitero San Nicolás, marking the historical boundary between Castille and León, and the Italian religious albergue (Ermita de San Nicolás) just before it; the Romanesque church of San Martín in Frómista which is just spectacular, probably my favourite church on the entire camino except perhaps for the cathedral at Burgos; starting to walk before dawn each day and seeing deep red sunrises every morning ("blood has been spilled this night" - Legolas); and the towns of Castrojeriz (especially), Sahagún and Mansilla de las Mulas.