[gentoo-user] Skipping world rebuild with profile 23.0 upgrade?

[Nikos Chantziaras]

So what happens if I skip the very last step in the profile 23.0 upgrade 
guide, which is:

6. Rebuild world:
   emerge --ask --emptytree @world
Is this just a security concern due to the new hardening flags, or are 
there ABI concerns?