I like Lucian. Played 1 Normal and 2 Ranked. 1-1 in Ranked atm. I think he'll become very popular very quickly. He actually does really good dmg, I was quite surprised since he is so mobile I expected a long ramp-up time before actually being able to do damage but I actually believe his level 1 rivals damn near anyone. His passive is way too strong. (After every skill you use, his next auto attacks twice). So basically you can Auto-->Q-->2xAuto = so much dmg. Also rotating abilities and 2xautos in teamfights and for taking down structures. Can chunk down turrets pretty quick. Not to mention the 2xAuto will apply any on-hit affects 2x as well, so double the lifesteal/BotRK etcetc.
Then you have his great mobility, he can dash out of danger which also cleanses slows (not stuns). He has decent wave clear with his Q/W, which also means he can harass in lane.
The one main issue with him right now is that his Q is bugged and will sometimes cost 2x the mana, this can be crippling, I found myself low on mana at the worst times. It's not fun using Q 1x and having about 20% mana lol. I almost want to buy a tear on him so I can spam abilities and keep rotating the passive autos but right now I've mainly just focus'ed on a high damage build. BotRK --> LW & IE --> Shiv/PD
Although his ultimate scales with attack speed, I'm actually NOT inclined to build much attack speed on him since the way I want to play him is by utilizing his passive as much as possible. My 1st ranked game I went BotRK-->LW-->BF Sword and was doing great other then the fact my team was feeding hard. (0-12-4 support, 0-8 mid, I went 5-7-3, which isn't a good final score but had participated in 8 of the team's 12 kills against really fed opponents).
2nd ranked game I went BotRK --> Shiv --> IE --> LW. I actually regretted buying the Shiv. It felt much weaker. My support in this game also fed but not as bad as 1st game, my support died 3x to enemy Twitch, I didn't die at all in lane phase. The mobility was too strong, was able to avoid Zac ganks multiple times and keep safe. Eventually we win and I end up 6-6-10. Still too many deaths but 16 kill participation isn't bad.
I want to try a couple different setups with him, always starting with BotRK just because it makes too much sense not to.
I'd like to try a "blue" build: BotRK --> Manamune --> Lizard Elder --> Iceborn Gauntlet. Basically go crazy on-hit and kiting, also the Manamune to remove mana problems.
Build#2 I'd like to try is more of an MF-ult-bot build: BotRK-->Black Cleaver-->IE-->Last Whisper. Basically high damage, high armor pen. His passive allows you to stack up BC insanely fast. 1 rotation is like 3 procs of BC.
I can't see any reason atm to even buy Shiv/PD unless you just want to have a stronger ult, which is fine, but he seems to play more like an ezreal where his abilities drive a lot of his damage actually. (Edit: I believe every attack of his ultimate also applies on-hits so that's another reason to get on-hit items over attack speed imo)