I have a lot of fun playing him. Early game you are playing a bit from behind, having low to average base damages. Your goal is to gain power by last hitting minions with your Q and hitting enemy champions with skills, which permanently give him one ability points each. His scalings are very good though, so end game you end up being a raid boss that can nuke anyone that you can hit.
Save your E for ganks or situations where you can play safely when it is on cd. Don't be afraid to delay your build with a couple of cheap defensive items like seeker's armguard or negatron cloak if you are starting to lose bad.