Pros-
Amazing at harrassing
All out great late game champ when using this build
Good for cheering by owning people you loose a couple of games
Good skillset
Focusing her in team fights does absolutly nothing when she has full build

Cons-
Fails if you play too aggressive early game and die a lot
Stuns **** her up
Her boobs aren't the size of Akali's or Nidalee's

Once you get Nashor's Tooth ( or if you lucky when you get Guinsoo's RageBlade) you start to deal a lot more damage. When your in the lane, you want to stack up the Guinsoo's Rageblade's passive then when that is at 8 stacks, you go in with your Q > E or W > Q > E combo for some good harrass. You use this same combo for kills in lane. You can turret dive sometimes but if you going to, make sure you don't use your w and make sure you have your ult in case. You want to save your w because it will heal some of the turret damage and give you a speed boost out of there. If you have to save your life then use your ult. If you have full hp and they have less then 25% of their hp, then i think its alright if you use your w and you don't have ult.

I max e first so the harrass damage is greater, but sometimes I'll max the q first for tiny harrass and if their getting too close to you all the time.

Teleport- I take this because you can teleport back to your lane, teleport to gank bot or top lane, or teleport to lanes to split push (late game kayle's split push is narly)

Flash- I take flash just cause it saves your life or sets up kills really good. you can flash Q people for a surprise then burst them down.

You can split push like a god late game. Through out the entire build I've been saying that she's good late game. Farming is where it shows the best. Don't think just cause she's really good at farming that she sucks at killing people. She is good at both but shows in farming. You can take out 3 waves of creeps when their around each other in about give or take 10 hits with e. Your w let's you move fast through the lanes so your creeps can still catch up but you'll finish the creep wave by the time they get there.

With this build Kayle can split push like a pro, duel people and make it out with more than 50% or 75% of hp, take down tanks faster than anyone else on your team, take out turrets super fast, and troll people on your team really hard by ksing them everytime. You want to pick kayle when ever you feel like it during normal or when the other team doesn't have a mid lane champ with a combo that starts with a stun in ranked. Getting mercs is alright if you dont have a choice when aginst a stun champ ( for example: veigar ****s you up) but it lowers your atk spd a bit. I wouldn't suggest switching out beserker greaves for merc unless your dying everytime to it.