Which chat service do you use?

My friends and I switched to Hangouts when it came out and now we are thinking about trying out a different service. Hangouts is nice but it's pretty buggy on iOS and not being able to use a chat client on desktop is annoying. We do a lot of group hangouts with lots of images and gifs and it can get pretty laggy on the browser. We are looking for something that is cross platform and looks nice, and obviously can handle group chats with images and gifs. What service do you guys?