Friends and passion for self development.The good thingsThe environment really gives you a place to belong where work is stress free and everyone have each other's back. A really good place to grow your skills and also soft skills, but it's competitive, in a good way. If you have passion for server and don't mind the working period, it's a really good place. Give it 3 years or so, and you will really miss this place badly.
The challengesLong working hours ? Nothing else I guess, because the feeling of having a second family makes up to it.