The best part of it is having Gmail on Android notify you only about important messages. It's great to get notifications about emails from friends about things going on tonight, but not get bothered by email list messages that can wait.

I've also found the "important" filtering very useful. It's fairly rare now that I get an email that really matters and is not marked "important". I think that it takes a while for it to figure out my patterns (yay for machine learning), but after that it works great. I bet most people just weren't patient enough to train it properly. (Of course some may just have more complicated ideas of what an important message is than me.)