It depends what you want to do with your cat. Evolution is an excellent bossing skill if you happen to be an AP cat. Personally, I like 4114 pure AP Primadonnas due to bossing being the only thing I like to do.
Evolution is ALWAYS a must for me when it comes to cats, but that's usually because my cats are always pure AP. The skills isn't really so amazing outside of bossing to be honest. Bosses are literally the only place I ever use the skill at all.