I really love Ajani because he's a powerful toolbox that falls at the right place on the curve for the decks that will use him best and he never feels too oppressive. 5 mana is a big chunk in my low-curve-centric format, and he doesn't pump out creature tokens, so that's great, too. It's true that he's so good that you don't need a +1/+1 counter theme in your deck to make him good, but he's crazy fun when he can show up in those decks, and he's pretty much one of my favourite walkers now.