This is going to be reasonably short, and you can tell what this is about from the title. Basically, I want to put forward the case that Spirit Stone and its upgrades are viable in lane. I'm going to argue the point from the perspective of me playing a particular champion. That champion is Cho'Gath.

So, first up, I want to talk about Cho and how he lanes. Cho'Gath sustains really well in lane, as his passive gives him health and mana back every time he last hits. My personal playstyle with him is to go as tanky as possible, buying minimal damage items as I believe that the base damages on all of his skills, and the bonus on-hit damage from his E deal enough, without AP scalings. Not to mention, his ult does TRUE damage. He has plenty in his kit, even without buying AP.

When I lane Cho'Gath, I like to rush a Philo stone for that gold/10 and sustain. This really fits my personal style as when I lane, I prefer not to "win my lane" by killing my lane opponent over and over like say, Darius would. I prefer to just spend my time farming my lane for as long as I can, taking the enemy turret down when I feel strong enough to be really effective in teamfights. Of course, I will go for kills if I feel I can. I'm not THAT passive a player. This playstyle suits Cho'Gath reasonably well, as I can sustain and stay in lane for a really long time.

This is where the Spirit Stone comes in. First of all, it's cheap. At 700 gold, you can quite easily buy it whole on your first or second back. Cho passive + Philo + SS will give you a lot of sustain. It will be very, very hard to kick you out of lane at this point. Say a Darius chunks you for 1/4 of your health with a max range Q and a couple auto attacks. Get a few last hits in and you are already back on full health. By repeating this process over and over, while trading damage back after each trade you bait out, you will eventually be able to whittle your lane opponent down while still retaining most of your health and mana. The only ways you will be forced out of lane is if you are going to be dived by multiple people or get 100% killed from any number of people.

My second argument for it being viable in lane is that it builds into good items, regardless of your role. Top laners can use the Elder Lizard just fine. Teemo for example can benefit from it. Tanky top laners, like Cho can build Spirit of the Ancient Golem and will have sustain, health and CDR just fine, also allowing them to forgo Mercs for other boots, as the item also gives Tenacity. Mid laners like Fiddle can make use of the Elder Wraith item thanks to the spell vamp it provides, and the mana regen can only be a good thing. Basically, you can use the upgrades to Spirit Stone as mid-late game items with little to no drawbacks.

Finally, there's the argument that the increased damage to neutral monsters is wasted in lane. This is not as big a deal as people make out. Sure, in lane, you won't benefit from it. But that doesn't make it wasted. The general effects of the items are all very good anyway, I can imagine people buying them as normal lane items if that passive wasn't on them anyway, it's just that dealing more damage to neutral monsters makes people think this item is for the jungle only. It's just a psychological barrier people put in the way to stop them theorycrafting. But why is the passive not wasted? Mid laners like Mordekaiser spam wraiths a lot. The increased damage will make doing that quicker. Sure, he's a slightly dodgy example as he doesn't benefit from the mana regen, but clearing wraiths faster between waves can only help. Fiddle is another mid laner who can use Elder Wraith and clear out wraiths easily, especially with the +50% damage to neutral monsters on his E. If a top laner like Pantheon uses Elder Lizard, he can farm his jungle and counterjungle the enemy team more effectively and therefore, safely. I build Anciant Golem on Cho'Gath for obvious reasons. When on purple side, I like to ask my jungler to leave double golems for me so I can go and Feast on them between waves, stacking my health more easily. Dealing more damage to those lets me get back to lane a little faster in comparison to a Cho who doesn't build the item.

Finally, regardless of which champion you are building which upgrade to SS, your team will clear Dragon and Baron faster as you have that increased damage. Therefore, those objectives are slightly safer as your team may have the damage for it when you otherwise would not (this especially the case when building them on high dmg champions, as 15% of lots of damage adds up to more than 15% of little damage).

To end, I want to sum this up simply. Spirit Stone is viable in lane as it gives you sustain, is cheap, works on almost every champion and still allows you to build into the later parts of the game with little drawbacks. This item and its upgrades are not only for junglers.