I bought all three today. The only movie I'd seen off of any of the discs was Creature from the Black Lagoon.
Earlier today I watched "The Invisible Man" (which is an EXCELLENT FILM, monster movies aside) and "The Mummy," which I actually found to be a quietly sad film. It's essentially the story of a man obsessively in love, who seems like he would normally be quiet reasonable about the whole matter had he not spent 4,000 years cursed to a living death. You have to feel kind of bad for Imhotep, despite all the bad things he tries to do.
Looking forward to watching the "lesser" films of each series. "Invisible Agent" sounds like it may actually be pretty cool.
Now I just need to go back and retroactively pick up Collection 1.
Hopefully they'll release some of the other, non-legacy Universal Monster movies on DVD like The Phantom of the Opera, The Hunchback of Notre Dame, Dr. Jekyll and Mr. Hyde, The Mole People and a number of others.