I was pointed towards this DVD some time ago and must admit to some apprehension having heard Gruberova attempting the Queen of Night. (It was awful, the clipped high notes and smeared coloratura of an aging voice.)
I could have fallen off my chair when I heard her Casta Diva. And sung in the correct key (rare). Simultaneously sublime, moving and thrilling. The essence of Bel Canto in my opinion.
Now be warned, a 59 year old singing the role of a young Druid priestess gurning some curious facial expressions might be difficult for those new to opera. It wouldn't work in Verismo but Bel Canto carries the drama more in the voice than the physical stage presence.
If you love Bellini/Donizetti et al you *will* love this Norma. If you are primarily a Bizet/Puccini occasional opera fan I *hope* you love it and further explore Bel Canto.