Is it worth it for me to learn how to play kassadin.

He is a strong champion. He has a good landing phase and can farm well under tower. His Q gives him the ability to poke and help soften the blow if they try to return the favor. His W combined with Lich Bane can cut through squishy Champs HP. His ult gives him an easy way into and out of fights while helping to deal noticible damage. Overall he is a strong champ and is worth knowing how to play

I dont think kassadin is the same carry he use to be. If you find him fun and put a lot of time into mastering him, you can probably make it work. However, I feel you could put your time into a better champion. Kassadin is a champion theyve had balancing for...ever? He takes awhile to ramp up, so if you dont mind relying on your teamate for the first half of the game then go for it.

I mained Kassadin in Season 4 and I'm slowly getting back into him, he's definately a good champion to master, however as robton said, he is not the same carry he use to be, you have to play MUCH smarter than you use to have to with him. Meaning you can't carelessly cast Riftwalk into the enemy team and expect to get out easy cuz of the ult range nerf. However he is really strong mid/late game, as his early game pretty much sucks azz... If you do end up picking him up as a main I suggest the following build.

Core: RoA, Lich Bane, Boots of Lucidity, Luden's Echo, Rabadons Deathcap Situational: Void Staff, Mejai's soulstealer ( This can be god mode on Kassadin since his bases are sh*t and he mostly scales off of 200% AP in 1 rotation, meaning the AP from mejai's isn't wasted.