Dislikes: Turn undead. Really needs to be changed. It doesn't follow the unified mechanic and makes turning completely useless at higher levels. (Well, almost completely. Liches are easy to turn.)
Too much overall power. They're second best at everything, which is like a superbard without the skills.
Some lame spells. Find Traps? Holy Aura? (The latter spell is only useful in terms of monster spellcasting. By the time a PC gets it, they already have a +4 Cloak of Resistance and +4 Ring of Protection and they could have just used Magic Circle Against Evil for pretty much the same benefits.) Also, the ranged healing spells are pretty weak until you get Mass Heal.
Some overpowered or just poorly designed spells. Blasphemy and Holy Word, I'm looking at you.
Spending the first three rounds healing PCs because it's a hard encounter. This doesn't necessarily mean the PCs did something stupid.
Likes: Spontaneous healing. No need to lock up spell slots on healing spells. It lets you get rid of spells that turned out to be useless today, too.
Great spell selection, especially in terms of self buffs, death magic and defenses.
Great overall abilities. Good hp, armor proficiency, good saves, decent BAB.
Social skills. More of an NPC thing, but of all the spellcasting classes, only clerics have the social skills to make them leaders. No matter how smart a mage is, he doesn't make a good leader due to his lack of social skills. Of course, clerics rarely have the skill points to make this possible.
Domains. Not too restrictive like spheres were in 2e. I treat each Domain as "balanced within itself" and don't consider domain pairs to have some extra layer of balance on them. (To put it another way, deities are not assigned domains as some kind of balance thing.) A few domains, like the alignment domains, are lame.