It depends on the need. I wanted a Jynx with the new ice moves so I evolved the babies until I got one. Up 0 Down
I just view them as basic XP dumps. Evolve them, and they either become a prestiger if they get the right moves, or they become a "Fainter" Up 0 Down
I just got a Cleffa 97.8% Doesn't look like a bad pokemon just I don't have the enough Candies to make a Clefable =( I need like 10-15 more candy =/ Now If I see one on the wild I will definitely look for because I need candy now to raise .. Up 0 Down