I have a concern with the druid's ability to spontaneously cast summon nature's ally. At mid-to-high levels, it can potentially add a lot of creatures to an encounter, slowing combat and generating confusion. Additionally, the druid's player gets a disproportionate amount of the DM's attention each round (Now there's three griffons, and they attack, then my animal companion attacks, then the dire wolves from last round attack and try to trip, and now I'll cast another spell...) Who hasn't been at a table with that guy?
My solution is to roll wildshape and spontaneous casting into one ability: spontaneously cast beast shape and elemental body spells. Treat this as burning uncast spells to power a spell-like ability to assume the form of a natural beast or elemental being. This should allow druids a lot of flexibility without soaking up an undue amount of time and attention while maintining the flavor of the class. I would allow some of the character's magical equipment to remain effective in the new form, such as collars/necklaces, bracelets, anklets, etc, depending on the new form.
I've never playtested this (sorry), but I'd love to get some input.
~ notshown