Alot of what has been said is true:
Dislikes:
-Turning is wonky and very unbalanced at higher levels. Unless you happen upon a nest(!?) of Liches.
-Domains are character flavor like salt sprinkled on top of a meal; much more an afterthought than anything ground breaking.
-Uber-wide range of spells no matter what your deity (or lack thereof depending), which illustrates a clear power jump over wizards.
-A little bit of multi-class action (say, one level of fighter with a human) can easily blow things out of proportion.
-Suspect dogma for each diety. Few players are inclined to delve into the workings and theology of their character's beliefs, though this is more a working of people than the class structure. Still, When was the last time your cleric tried to convert NPCs? What benefit was gained from doing this, other than a warm fuzzy for role-playing well?
Likes:
-Spontaneous Casting. This is just a flat out great idea. In my opinon, this is unfortunately what makes having the uber-wide range of spells wonky though.

-While the sheer number of available spells still grates, the fact that many of them are defensive / team-oriented soothes that irritation a bit.
-Able to step up to the front rank if needed, take the hits and make the heals necessary to keep the group alive.
-Even with a few simple limitations (only spells & domains from PHB), you still have a very dynamic character.
I did like the way sphere's handled available spell choices. It doesn't always make sense that a god of Death would allow their clerics, who supposedly represent them on the Prime Material Plane, the power to heal someone.
I would suggest using a sphere concept for their initial available spells based on Diety / belief. Then, just like spell research grants them to you, additional divine spells may be learned from other casters, divine intervention, found scrolls/tomes, etc. Once they learn the spell, they then have it available to them.... unlocked it, so to speak. Perhaps some deities will punish those who share their knowledge with clerics of other deities that are not like-minded...