I hate to setup databases on local machines, so mLab is the best solution for me & my projects.
UI can be improved.
If mLab will add some features like phpMyAdmin has - it'll be killer.
But it's works and i'm fine with that.
mLab gave enough place for store some data for side-projects for free. And it's easy to use with heroku. Search "mLab" in heroku addons and chose "Sandbox" and you'll have a custom url to your database