I liked that it is available for both desktop and mobile, which was important to me because I'm traveling often and want my bot to be around when I need it! Not much - maybe some better documentation? It's not too bad but you have to use their code editor if your looking for something more robust (like we're doing at work).
They are constantly improving so I would keep an eye out for new releases. My team can now easily build bots quickly using our own custom domain names instead of paying through the nose for one from Google/Facebook etc.