Gwen has almost no weaknesses and when played perfectly, she's flawless. She has an extremely overwhelming early game and just continues scaling from there. I've been bullying lane bullies like Reneketon. She can even beat champions that were specifically made for early game like Lee Sin with ease. Once she hits 6, she's basically impossible to duel. Her ultimate allows her to 1v2 with ease and even 1v3 when played out correctly. She's a good teamfighter because her W forces a fight with a frontline for 5 seconds, and that's enough time for Gwen to burst them. She has a good engage with her Ultimate that slows, and can disengage if she thinks its a bad situation with the rest of her Ultimate charges. Gwen scales! She doesn't fall off! Gwen does more damage late game because she has more AP. (Don't say duh and keep reading so you know why I said this.) Her passive does an additional 0.8% maximum target health damage for every 100 AP she gets! If you want to just keep things simple, think about early game Gwen and a late game Gwen. If you played her, it's obvious that her late game is stronger than her early game. Her actual real weakness is that she just relies on her Ultimate and W to win fights. If she has her Ultimate and W. She can literally kill the enemy team alone (I know this from personal experience!). Without them, she's vulnerable and isn't as threatening against an entire team. You can't just send someone weak to waste her ultimate because she won't even need it, but if you send someone strong, she'll use her ultimate but with that one strong person off the map, it limits your choices. If you send the whole team to kill her, there's multiple things that can happen. One, her team will be nearby and will end up destroying your entire team. Two, if she plays the fight perfectly, she'll end up 1v5ing the whole group, but even if she doesn't she'll get some of your ultimate abilities, summoner spells, etc. Third, her own team can just be trading Gwen for objectives like towers, baron, dragons, all that stuff. If you wasted your spells and stuff after fighting Gwen, that puts you in an even worse situation.

This one is actually really easy to explain. Since she's still new, players don't know how to pull out her full potential. Gwen requires you to play perfectly, and you need the precision of a barber cutting someone's hair (haha). She is so good right now, I really recommend you pick her up to climb before Riot nerfs her. First off, since she's still new, players trying her out might not know how to bring out her full potential. She is challenging to learn, but that challenge is worth overcoming. There are more noob Gwen players than experienced or one trick Gwen players and those noob Gwen players drastically lower the win rate. Second, Gwen really takes a while to master and require a bit of an above average knowledge of the game to be able to play well. You need to know what fights you can win and how. An example of a challenging thing while learning Gwen is when you should use your W. Gwen's W is what makes her OP because when utilized correctly, she can 1v5 with it. The timing of her W is so important, it can mean the difference of life and death for you. If you wasted your W on a single Ezreal Q in a teamfight, the enemy Zyra can just stall your W and then do her combo on you. Gwen's high outplay potential is just something you have to learn while playing her. I am 100% confident that you will never master Gwen in a single game or a single day. I've been playing her non-stop ever since she came out and not even I know her exact limits. I know what she can do, but I've just been scratching the surface of what Gwen is truly capable of. Maybe you can?

Common Problems Gwen Guides Express And Proving Them Wrong

Middle Q is Hard To Hit!!
I don't really see how you miss a line that's directly in front of you. You have a dash that can be used to hit your Q, or follow someone's dash because you can use it while in your Q animation. A fully stacked Q takes less than a second to pull off and whenever I play Gwen, I don't struggle at all hitting the middle of Q unless the target has 400+ MS. (If they're hard to hit with your Q, they're hard to hit regardless, its not her Q that's the problem!) Gwen has her Ultimate to slow, her E to dash, and she can even build things like Rocketbelt or Everfrost to help you land your Q's. Because you have all these things to hit the middle of your Q, I'm sorry to say this but I really think its just you if you still struggle to hit Q. I know this is a little bit more challenging in high-elo because players have better positioning, but in low-elo, you can easily land your Q's sweet spot because low-elo players don't acknowledge the power of positioning.

Maxing E First
I strongly think that maxing E first is wrong. I cannot express this enough. You need to max your Q first so you get more damage output! A max Q is on a 3.5 second cooldown which is turned into 3 seconds with agility haste from your items. Q keeps you alive with the healing you get from your passive and it's the main source of your DPS (besides your Ultimate). Here's a tip that I'm sure only one trick Gwen mains know. Gwen can Q before she gets CC'ed so this completely turns half of your counters around. Jax E stun will last just as long as a fully stacked Q from Gwen. This heals you, damages the enemy, and most importantly, it ensures your not just standing there for 2 seconds. Maxing Q first just has more benefits than someone who maxes E first.

W Is Useless In Top Lane!!
Some guides might complain that W doesn't do anything at all in the top lane. When your fighting, in your W you get an extra 20 (plus 5% of your AP) armor and magic resistance. This is basically saves you 300 gold from buying a cloth armor or 450 gold from buying a null-magic mantle. This helps you win fights you already win extremely hard. If you position your W right, you can damage the enemy champion right on the edge of your W area. This can bait a spell or two (like Mordekaiser Q) and lead into an all in. If they try walking in your W area, you'll win the trade because of the extra armor and magic resistance you get.

I have over 100K mastery points on Gwen and already have 150+ games on her so I really think I know what I'm talking about. Ultimately though, this is all just my opinion. I don't mean to offend any other guide creators, I just want to speak my thoughts so we can all learn and become better at Gwen together.

If your interested in learning more about Gwen, here are the some guides I personally enjoy and my own guide...
ForgottenProject's Guide

PH45's Guide

SirGRC's Guide

My Guide