Within core, they might not be "the best" but they're very strong. IMO Natural Spellcasting is overpowered.
Wildshape has gone through so many permutations I wonder which version each person is using

The oldest version that I recall let you keep your items while wildshaped, which wasn't good for stealth (look, that squirrel has a magical cloak!) but now you can't do that. Alas, that means that some items you shouldn't lose* (like your Periapt of Wisdom) get lost and that causes all kinds of annoying spell loss. Still, the newest version lets you fly and cast Summon Spells and Call Lightning (Storm) on the sly. IMO the summoned animals are superior (in terms of raw combat) than fiendish/celestial animals, although their Int 2 and inability to communicate reduces their usefulness; but then druids can summon elementals spontaneously, along with unicorns.
* If only because it adds complexity to the game. IMO, you shouldn't gain or lose spell slots unless you've changed your ability score for 24 hours. Now, if you wildshape
all the time...
IMO, clerics have the edge due to having a better variety of spells, but druids
do have good spells in most areas. In a dungeon, the druid has fewer useful spells, but still has many that are useful. IMO, one of the biggest problems with a druid is taking your Int 2 animal through some really harsh dungeon. Let's hope you maxed out your Handle Animal when you have to run alongside your companion through the smoke-filled hallway o' doom!
el-remmen said:
Wildshape abuse is easily countered by ruling that they can only adopt of the form of creatures they are familiar with. . . Never seen a dire bear? well, you can't turn into one.
Dire bears aren't broken, so I don't see why a DM can't use them. (They might be a tad under-CR'ed, but Wild Shape is way too flexible for balance.) If the DM can't use a reasonably balanced monster because of a player ability, I don't blame the monster ... or even the DM.