I'm actually a fan of them changing the Raid Bosses... With the exception of a few. Metapod as a boss is beyond silly. And the same goes for Sableye. We just had an event bloody full of them! There's no way I'll do one. The evolved starters from Gen 1 are good though. I'm still looking for a Venusaur, so this bodes well.
My brother pointed out something interesting today though. Apart from 2 or 3 Pokemon, all of the raid bosses are from Gen 1. More proof that they'll eventually phase them out as Gen 3 becomes more prevalent.