A small explanation about the potion in the special · 7:02pm Aug 7th, 2012
The love potion is just as the show explained it, the people who drink it together fall deeply in love with each other and will refuse to turn away from each other's eyes. The fact still remains that they have to stay away from each other for one hour for the potion to cancel out.
Now here's what I added.
If the potion is consumed within a group of three or more, the potion will run rampant and will make the victim fall in love with the first person's eyes they meet that had ALSO drank the potion (This is why Pinkie didn't gun for Soda, but instead Shadow) It is indeed possible for one victim to fall for another who is already targeting someone, as well as the victims switching between who they ":love" at random.
There is also a newly added factor that the potion is Equestrian only, meaning it only works on PONIES. This is why even it was the love potion, nothing happened between Spike and Rarity out the usual. Which leads to special case of Winston and Shadow. They technically are Equestrian, but at the same time, aren't. So when he drinks the potion it's only at half capacity, making merely attracted to the eyes of the other victims and not outright fall in love. The only perk of this is that now he can see all the hearts and can tell who drank and who didn't
