Not any more. As far as I can tell, old .asc files run fine on the new version.
Seems fine to me. What problems are you seeing?
I suspect that other people wrote the Analog Devices models. They look rushed.
Again, XVII seems fine to me.
XP is ancient and I remember it being very flakey. Win7 is very solid. Every 5 or 10 years, you've got to upgrade your hardware and OS.