Smite in lane... Troll or legit?

Note: I mainly played this top lane (and still testing it out) but I am considering something new - smite ADC or smite support.

For top lane, I have tested Challenging Smite on Shen, Yi and WW with varying success. It didn't work so well on Shen, but on Yi and WW it felt like a decent alternative to ignite (i ran ignite/smite on yi though hehe).

But after jungling with Vayne, I started wondering: A 60 second CD true damage steroid, damage reduction and vision, wouldn't it be a decent alternative to heal or ignite? It would be considered an in-between option for offense or defense, as its defensive power is inferior to heal and its offensive power is inferior to ignite but it has offensive and defensive capabilities, with the added utility of vision. However, it scales off attack speed, while ignite doesn't scale which makes gives it 1 advantage over ignite. Wouldn't this be a good option for champs who autoattack a lot? (i.e. ADCs?)

As jungle Vayne, I needed it since I was farming (and getting Devourer synergizes with the Challenge Smite passive). So, the 750 gold sink did not exist for me since I was getting its worth back through Devourer. As for lane, the question is, CAN AN ADC AFFORD TO SPEND 750G TO BUY THIS STEROID? I do question its worth for bot lane since bot lane usually lacks 1v1 duels, making the single target damage reduction less effective than it is top lane. In top lane, attack speed duelists suddenly gain a power spike for all ins as soon as they get the item, which makes the buy worth it in my opinion.

For supporting, I only had 2 games because I normally got forced into the jungle with smite. But I found that I could run Exhaust/Smite on Shen support somewhat decently, getting Chilling Smite to turn him into a CC machine. I find it somewhat OK because Stalker's Blade can be Juggernaut enchanted for 500 HP, 10% CDR and Tenacity, which is not a bad item for tank supports. It helps me smite those cannons for my targon's when my ADC doesn't let me have them too :3

As I haven't had much experience myself, I'm interested to hear from anyone else who has tried bringing smite to lane, and your thoughts on it.