Their coding challenge was straightforward and not impossibly hard like some other companies'. The questions are just meant to see if you have some fundamentals of programming. The phone screen and on-site interviews were not overly stressful, and everyone at the on-site interview was very nice.
What I wish was different
I wish I could go back and see the responses to my coding challenge.
Advice
Practice in a language you're comfortable with they don't require you to use their specific language.