From personal experience I see that every top had its limits to there power (resource management, high cooldowns, etc.)

What I see in Riven is that she has it all, high mobility, passive tankiness, no mana or any resource at all, high damage, scales great, good at all phases of the game, hard to gank, good burst, no high cooldowns, and strong team fight presence.

Am I missing something here? Jayce had and has his limits, and so did every top. But Riven? All I see is lack of harass isn't that a bit much to put in all one champ?

she is one of the only tops that has nothing but physical damage, and she has no ranged

those are her two weaknesses (granted with BC the physical damage part isn't near as hampering as it used to be)

range
spammable CC
lane freezing
dont become reliant on your towers
Dont become reliant on just one of these

Dont get ganked while she's at melee range

Her weakness is Garen, and Draaaaaaaaaven.

She's CD reliant as well. Bait her into doing her Q combo, or even blowing all of her moves.... dodge/run away... then you have like 10 seconds where she cant do anything to you until her CDs are back.

Riven is cute so she gets it all. Any further questions?)

Being serious though, she is reliant on her abilities, since her mobility and most of the damage come from them. Once she used everything she is there to be killed. Also, her gapcloser range is shorter than most champions so she will have to use other skills too, in most cases. Which leads to first problem. Also, Riven usually builds quite squishy for early-mid game.

As previously mentioned, armor and ranged attacks are Riven's primary weaknesses. (So no, I don't consider Garen a counter to her.)

Her mobility is high for a melee champion, but it isn't "all in one go" like Xin Zhao or Wukong. She can still be kited by many ranged champions.

Thirdly, as was also mentioned here, Riven's entire trading game revolves around her abilities. If you can get her to waste one before trading, you'll probably win the trade.

See, Riven's game is played this way - she engages on her terms at all times. A good Riven will put you on the defensive and keep you there, at which point you've already lost the lane to her. However, if you can scare her a bit, get her to play more defensively, it goes a long way toward beating her. Especially if you can poke at her.

Garen counters her is because of silence, silence rapes her since she needs to spam abilites. A single Q + Spinning on top of her would mean by the time she can fight back she took a **** ton of damage. If she does fight back, you'll just push W and get a massive armor boost.

She loses to other champions that are mobile with crowd control or large amounts of armor, as well as being CD dependent.

from what i've heard teemo is a major weakness to riven good harass and his blind cancels her passive not impossible lane but that might change with her nerfs.