Older binaries X11 quake for instance will not run on redhat-7.0 beta. They at least try to execute with /usr/i386-glibc21-linux/lib/ld-linux.so.2 but with /lib/ld-linux.so.2 they just give ld-linux.so.2 a seg fault. The glibc-2.1.3 compat loader gives a libm.so.5 not found because of the elimination of libc 5 compatability. It seems to me this is a rather bad move, since there are still some programs out there that are binary only and linked against libc 5. I suppose I can just install the compat package from 6.2, but this is a pain.
If you really want to run libc5 applications, you really need to install compat from 6.2, I don't see any point in shipping libc5 compatibility forever in the distribution. glibc is used in the distribution for 3 years.