Stormcast are one of the most versatile armies in
AoS. You can gear an army towards melee or ranged, pseudo swarmy, or hyper elite. They have a wide variety of good units and competitive formations. That being said, their traits and artifacts are pretty hit and miss, with Staunch Defender being held as the almost universal king.
There is a great (and quite extensive) thread on TGA discussing
SCE. It has been running since the book dropped and is still active. Definitely worth a look in your free time.
http://www.tga.community/forums/topic/6037-lets-chat-stormcast-eternals/