I play since season 6 and I'm otp Evelynn all those years before and after her rework. The reason I loved this champion since I start playing LoL is her camouflage which makes her very special. I'm level 7 since before her rework but I would also be lvl7 even after. I have more than one and a half million points on her and I only play her unless she's banned or picked by an opponent.
There are a lot of good and in depth guides out there from much better players. My goal is to share my experience playing Evelynn against every single champion as my guide title says.

Pros
High Burst - Oneshot kills
Great sustain and fast jungle clears
Excellent tower diver
Can make easy kills to get fed

Cons
Tricky positioning
Weak early game
Very squishy
Hard to come back if behind

I pick Evelynn no matter what because I'm otp and I rely so much at camouflage that I'm not competitive with any other champion. Although, you should avoid picking Evelynn vs 3+ tank teams while you have one or none in yours or teams that have 2+ champions with counter abilities for your charm such as Vladimir's Sanguine Pool or Akali's Twilight Shroud or Fizz's Playful / Trickster or your team has already 3+ Ability Power based champions and opponent team has 2+ fighters/tanks. In any other case you can freely pick Evelynn to carry! ;)