In answer to the questions posted:
I like the VZ grips a lot. They look great, but they also feel a bit more comfortable. Honestly, I bought them for the looks. Although the rounded edges do improve comfort, I wouldn't replace the original grips for that reason alone. And, I have no complaints about the original grips. Just thought I would give the VZ grips a try, and I liked the end result.
Regarding the screws, the VZ grips come with their own set. I used lock-tight, so I can't easily dissasemble to try the original screws to see if they fit. Sorry. But I would think you would want to use the VZ screws anyway as they fit and match perfectly, and you could save the original screws with the original grips for future use or resale value.
The real improvement in comfort is the result of adding the mag extensions from John (Yankee2500). I shot about 150 rounds through the gun before adding the extensions, and the recoil was punishing. The extensions allow for a much more secure grip, resulting in much more manageable recoil. I have shot another 150 or so rounds since adding the extensions. Much more comfortable! They do extend the width, but as you can see from the picture, it's still a very compact package.
Oh, and I did replace the spring as per the instructions. I can't imagine it is really necessary, but why take a chance.
I really love this little gun. It's just so dang beautiful. And it's dead accurate at 10' to boot! Thanks for all your comments.