I've had the DVD box set for a couple of years now and I'd have to say that the bonus disc is full of collector's items, but no more than that. I have watched all of the deleted scenes and to be honest, I think the cutters got it right with just about all of them. They serve no real purpose in themselves in that they do not offer any information to the viewer that is already present in the cinema versions.
With regards to the hospital scene, it would have slowed the plot down too much. After the opening extravagant wedding scene, the pace is unabating until Michael shoots Solozzo and McCluskey, even if the Woltz encounter is a bit of a diversion.
And as for the introduction of Roth, I think the sight of the slightly gawky character would have diminished the presence of the monster who appears in the later scenes.

By the way, I have still to watch G III !