My Multi tank isn't all that special, it's about 45 liters, 12 US gallons, and I have four Multis. I'm quite positive that I have one male and three females. There's a java fern attached to a rock in there, too, but I think I'm going to move that to the shrimp tank and get some Vallis, as I've been reading there is a plant similar to the Vallis in Lake Tang. Anyway, to the snails...
I have two possibly three different varieties of the Sulawesi snail. In the Multi tank I have three long and large black coned snails (about two inches long), and then a smaller black snail which is about an inch long. In my shrimp tank I have two yellow coned snails maybe around an inch and a half long. The black coned snails, are pretty easy going, slow moving, slow eating, and they tend to 'hibernate' a lot, where they basically withdraw into their shell or just stay in one spot for a day or two. The yellow coned snails, are pretty much the exact opposite. They move around A LOT, they eat A LOT (which of course means they poop A LOT), and they also will eat any of your plants. However, both yellow and black Sulawesis are not to be relied on to keep the algae down. The pond pest snails are better at it than they are.
As for the Sulawesi's relationship with the Multis, everything seems fine for the time being. At first the Multis were quite territorial with the Sulawesis, pecking at them, and even trying to pick them up, successfully on at least one occasion, but now they must not see them as a threat too much. The snails are allowed to get closer and closer, last week one of them was cleaning the outside of a shell-dweller's shell, and just yesterday I caught another one inside the shell. I'm a bit concerned about the Sulawesi's trying to eat the fish eggs, but seeing as how they don't have a taste for the pest snails eggs, and shell-dwellers being notorious protective parents, I'm hoping it will be alright, not that I think I have eggs right now, I've only had the fish for a month.
Personally, I like the look of snails in a tank. You never know where you're going to see them in the tank, on the sides, on the floor, climbing up the plants, it's always a 'Where's Waldo?' situation. And because my Multi tank is so small, where I could only comfortably have the Multis and no other biotope fish, the snails are a good addition to clean up the leftover food, (as I've noticed that the multis don't go very far from their home turf for food.)
Anyways, that was probably WAY more info than you wanted, if so sorry.