I use OS X 10.10.3 here at work, and my colleagues use Fedora 21 with Gnome 3.14.2.
I use apps like Mail and Telegram, and OS X give excellent visual warnings about new messages (numeric badges in the app icon at the dock, sliding notifications that can be set to stay there or disappear, notification center, etc.). But Fedora (as it comes) is terrible to warn them about these things! Both Evolution and Thunderbird show a temporary and tiny message at the bottom, and then it is gone forever. Telegram displays a much bigger message, but it also disappears after some time.
Those problems get even worse because they use two monitors. And some mail/chat messages are really important to be seen as quickly as possible.
We can make some dirty hacks like redirect the mail to Gmail and have a browser plugin to show the alerts, but I was hopping to find something more native. If necessary, we could also try to switch to KDE.