I bought this set when it came out, but never got around to watching them until now. I'd seen the first 2 years ago(sometime in the seventies), and the third one several years ago.
I thought blu-ray clarity really showed off the poor blue screen work in the second movie--Special effect wise, I thought the 3rd looked the best.
Very high quality transfers in my opinion.
As far as the movies go, they were as good as when I'd seen them before, but I had never noticed what a bad actor the little kid in the 3rd movie was(as jellydonut25 mentioned). Several times when he should be sad or crying, he's smiling--almost made me laugh a couple times.
Definitely would buy these if you don't already have them.
The future is big, sparkling warble of superclean and we should endevour to do our best to wash our feet by it.