Isn't CPAN for Perl ? I don't actually know CPAN. All I'm saying is that having a package manager that doesn't allow removing packages is an advantage IMO.
CPAN packages can't really be uninstalled (http://stackoverflow.com/questions/2626449/how-can-i-de-inst...) and seem to be unnaturally prone to dependency hell.
The concern about running the entire test suite on module installation really isnt a problem if you think about. Additionally you are able to force the install if it fails on account of a test.
While that behavior feeds back into improved quality for responsive maintainers, it takes additional time during installation. When combined with point #1, it can make dependency chains seem more fragile.