Well, first off there's the initial benefit of having an animal companion, a loyal friend. Now comes the interesting part, when opportunaty strikes for your snake, you take it. Let's say your travelling along a trail to yet embarke on another adventure, when all of a sudden you spot a family of farmers, who happen to have a rat problem, and let's say your faithful slithery friend hasn't had a good meal in a while, so, kill two birds with one stone, show off to your fellow party members that having a snake along side you is good, and possibly get a free meal and a rest for the night for your sudden generosity. Now, lets say you've taught your faithful serpantine friend how to identify and search for different types of plants, lets say you character is at a really high level now, when all of a sudden your party has been stricken with dumbwombe, causing your bones to bend in akward places, and there's no one around to save you, and your too week to move to attempt to gather the type of plants conviently located in the forest next to you. Since snakes are immune to this disease, you can have your faithful animal friend gather up the plants you need, problem solved. Now, these's encounters arn't likely to happen, but the point I'm trying to make is cease every opportunity you can to make the usuful traits of the serpant, and for fun, try improvising a little and see what happens.