I've Dm'd for a druid for over a year and a half now, from 1-11th, and I have found a Druid to be useful in some way in almost any circumstance, but not overpowering.
BTW I run a city campaign, so theoreticaly the druid is at a disadvantage,(though I find that to be hogwash).
1) Animal Companion: The animal companion is a nice benefit, basically a druid can be a pure stand back spell caster, and still get some melee damage done. Animals however have low ACs, and often times can absorb more healing resources then damage dealt. I can not emphasize enough how low animal ACs are, as this impacts SNA, Wildshape, and the Druids Animal Companion.
Tacticaly an Animal Companion is good for flanking bonuses, Coup De Graces, and whatever bonuses,(trip, pounce, etc) they have added onto their attack.
Role play wise the Animal Companion is a mini cohort, the druid in my campanion has spent quite a bit of time and resources on her various animal companions, even going so far as to buy and then enchant magical barding, and other magic items for her animal companion. Good thing druids can get by with less in terms of character wealth, because good role playing druids will probably spend money on their animals.
2) Wildshape: wildshape is a great abillity but probably not for the reason people think for. Any really open ended power like wildshape or polymorph runs the risk of "breaking" an encounter or letting a player do something unexpected. For me I like that as a DM, for other I can see how it is frustrating. Melee wise again animal ACs are extremely low. A dire lion has an AC of 15. At 11th level an AC of 15 is butter.
Creative uses of melee wildshaping often involve chosing a form with a good grapple modifier to prevent grappling. Then again if a mob is getting that close to the druid to grapple him or her turning into a large animal, may not be feasible space wise.
3) Natural Spell: not a big deal in my book, other than it is essentially a must have feat for a druid. A druid in Dire Ape form standing back and casting a spell, is little different then a druid in normal form standing back and casting a spell. Again, very rarely will you see a druid in wildshape animal form casting a spell while in melee combat, a blown concentration skill check for casting defensively almost absolutely guareentes enough damage being dealt that the spell will be lost.
Even a flying wildshaped druid is not that big of deal, since most animals do not have perfect flight, which means no full round actions when in bird form as the druid must move forward, which means no SNA, no Call Lightning etc.
4) SNA: Summon Natures Allies is great for creating flanking bonuses, or speed bumps to slow the monsters down. A warrior is seperated and low on hit points, pop a SNA, summon mutiple animals to distract the mob the warrior is fighting, and place them strategicaly to block movement. I have seen a druid literaly surround a giant with Dire Wolves with a judicious use of SNA.
On the other hand I have also seen that same giant using a two handed weapon, power atttack, and great cleave kill almost all of those Dire Wolves in the same round.
5) Spell list: a druid has a decent spell list but not amazing. Druids can heal and divine, but not as well as clerics. Druids can be blasters, but generally not as well as wizards. Flame strike is a great spell, but it has a very small area of effect, and column effect areas can pose difficulty especially if one has allies above the area to be effected,(say on a balcony 30 feet above). Druids have many great spells, perfect for extremely limited applications. Stone shape, Contol water, repel vermin, stone tell, etc are all great spells, but often ones that might go unprepared, or unused if prepared. As an aside one of the best 5th level druid combos is Flaming sphere combined with Call Lightning. The Druid can move the flaming sphere with a move action, and call a bolt with a standard action. Even with this you are looking at one round to cast Flaming Sphere, one Full round to cast Call Lightning,(and thus not move the Flaming sphere that round), and then spending subsquent rounds controling your magics. Effective but very time consuming. Frankly overall I find Heat Metal and Call Lightning pathetic spells, no wizard or sorcerer would willingly take them if given the chance to. Awaken on the other hand......
