Over here you an still find them on the shelfs, as Aoshima and a few companies do occasional re-releases.
For me the best Super Robot Kits are the Resin Versions from Volks and similar garage-kit offerings.
Have a look at Hobby Link Japan: www.hlj.com
You should be able to find quiet a few kits there.
As for fit and detail it really depends the old Kits were fairly low quality and had a few problems, some of the new stuff is very decent.