One-handed - Balanced. Dual weilding 1 handers is pretty useless becuase of the lack of block ability and the negligible damage increase. Otherwise Sword/Shield, Sword/Spell is a fun combination.
Light armor - Unless you are a primary caster it's worthless. Run speed has little to no noticeable difference, it's not lighter when you get the perk to make Heavy Armor weightless, not much difference for stealthing.
Sneak - Completely overpowered. 100% camo was overpowered in Oblivion the same for Sneak in this game. 1 shotting pretty much anything from stealth with a bow or dagger gets old quick. Oh yeah choosing Shadow Warrior may as well bring up the ending credits.
Alteration - Balanced as long as you get the perk to have unlimited duration time on your spells. Otherwise get very used to pausing your gameplay every 15 seconds to bring up the menu to cast a buff on yourself.
Smithing - Completely overpowered. For the low low cost of a few hundred iron daggers, you too can completely ruin the fun of looting, dungeon exploring, or quest rewards.
Block - One of the few balanced skills in the game. It requires timing to use which increases the user experience and is useful to use often.
Heavy Armor - Simply better than light armor in almost every situation even for Sneaks
Lockpicking - Worthless if you get the skeleton key. Still worthless otherwise if you have enough lockpicks and common sense.
Enchanting - The most overpowered of all the skills. Not only does it make finding items completely useless, but selling off enchanted iron daggers (which pretty much everyone figures out) breaks the fun of selling items for gold.
Alchemy - Overpowered. What's with the crafting in this game? At first it may not seem overpowered but at some point you will quickly realize that you can't ever die when you are holding 100 health pots, magic pots, and +dmg pots. Also 50g to make a pot and 500g sell back gets ridiculous.
Two-Handed - Balanced. Even though giving up the shield is huge in Skyrim, you aren't gimping yourself by choosing 2 hander. It's not over the top or underpowered.
Speech - Worthless. Gold becomes trivial by the time you can invest in this tree. Persuasion and Intimidate has little to no impact on a story line.
Pickpocket - Worthless. Either you pickpocket early with an extremely low chance of success of getting anything valuable or you wait for pickpocket items/potions and realize by that point of the game the items are useless.
Archery - Overpowered. It's terrible that no matter how you spec you will end up using a bow and arrow. Used from stealth and it's over the top. I just can't see Gandolf chasing a dragon around on foot with a bow and arrow.
Illusion - Worthless. Nothing in this tree is useful and even if it was slightly useful each skill is trumped by potions and items you find along your journeys.
Conjuration - Underpowered compared to all melee trees and your own companion. You already have a near indestructible companion at your beckon call. You can choose to forgo your companion so you can be forced to summon and blow your magika every fight but that seems more like a chore.
Destruction - Underpowered compared to all melee trees. If you aren't comparing then Destruction becomes a challenging tree that requires time and patience to kill each enemy you come across.
Restoration - Balanced unless you take up Alchemy. Then it becomes pretty useless. Instant full heal from Alchemy > Channeled heal from Resto
So in order to still experience the fun of having a decent battle and enjoy the item rewards you pretty much have to avoid the overpowered Sneak, Smithing, Enchanting, Alchemy, Archery. If you want to avoid placing your points in completely useless and/or redundant skill trees you have to avoid Lockpicking, Speech, Pickpocket, Illusion. This results in having to avoid 9 out of the 18 skills just to have that feeling you had in those first amazing 10 hours of Skyrim. The only problem is that you know you are avoiding these skills and it creates a situation even worse than the tempting option of using the difficulty slider. It creates a game where one wrong decision early in the game on skill placement results in the game not feeling genuine or fun after only 30 or so hours of gameplay.