I went into my boxes to pull out a complete book to analyze the kits and the first I came to was Elves.
The Herbalist is a priest kit. It does have none magical healing and that's pretty cool. I would not consider it to be a powerful kit though.
The archer, for the warrior, might be a bit powerful. They get extra shots or a bonus to trick shots. Their negatives of very limited in melee weapons is not that bad.
Wilderness Runner is one of those kits where a hindrance might not be enforced. They get bonuses to track, and can set snares as a thief. They have practically unlimited mundane equipment because they can make things from organic materials. They can't stay in cities, dungeons, crypts, or such places for much longer then a day though. They never use mounts, and have some negative reaction bonuses to civilized elves.
Windrunner: they gain a flying mount at higher levels and take negative reaction (jealousy) from other elves. Depending on how useful a flying mount is in a campaign would determine the strength of this kit.
Spellfilcher: can cast detect magic 1/day per level. And nice bonus to find and remove magical traps. They have to be part of a guild so if that is ignored or made to easy then it could be a very good kit.
Bladesinger: Good bonus to attack and damage, bonus to do cool maneuvers, a great AC bonus (especially at higher levels) when casting spells. However, the disadvantages are big when used. "They must lend help to any elf in need." Only use a single type of weapon so if it gets lost or taken, the Bladesinger could be severely hindered. It is a powerful kit but boy can a DM mess with these hindrances to really mess with a PC.
War Wizard: to take advantage of some of the benefits they really have to jump through hoops with ability to survey and map the battle field ahead of time, hold a strategy meeting, and make Int check. Of course the real special benefit is the spell of choice. They can cast it faster and give opponents a negative to save against it. Hindrances deal with a code of conduct and they are part of a unit. It is a strong kit but the hindrances like the Bladesinger can really take a PC out of the game.
Huntsman: Nice fighter thief kit. Bonuses are not that great (plus to stealth skills and can track) but hindrances are not much either (reaction penalty from everyone)
Collector: never used a charged item, never destroy a magical item; hindrances are pretty bad for this fighter/mage/thief kit. Can potential find items and know the history of magical items so could help identify what something is and that can be huge.
Infiltrator: lots of bonus non weapon proficiencies (5!). Better at disguising himself as another race. But slowly loses elven resistance to charm and sleep.
Undead Slayer: Kit for any class. Can prepare for undead and gain bonus to attack and damage. Has a really vague ability to find the area of undead liars. Will always face undead over other enemies especially intelligent undead. Something a DM can easily exploit.
The most powerful the Bladesinger I have seen in action. It is good but we still had fun with it and no one ever complained about it being to powerful. But I can see why people think so. Also, when combined with other optional rules for the Complete Book of Elves the class gets even better as the book treats elves as superior to all other races and backs that up mechanically.
