You can't judge a book by its cover, or a Linux by its interface. If you glance at Ubuntu 15.04, Vivid Vervet, you won't see a lot different from Ubuntu 14.10. Don't let first impressions fool you. Underneath that slick Unity 7.x interface, there's a lot of changes.
While the new Ubuntu isn't due out until April 23rd, the second beta is more than mature enough to see what we'll be getting in the Vivid Vervet. A vervet, for those of you who are wondering, is an East African monkey.
Based on my work with the beta over the last few days, here are the most important changes in Ubuntu 15.04. I've been using Ubuntu since the first version, 2004's Ubuntu 4.10. These days, I use it on desktops, servers, and cloud. In other words, I know Ubuntu.
1) Ubuntu switch init manager from upstart to systemd
Ubuntu's developers decided that, even though they were a few days past the feature release freeze date, they would switch 15.04's default to systemd. The change will affect "Ubuntu desktop/server/cloud and the flavors like Kubuntu, but *NOT* ubuntu-touch." Ubuntu Touch, Canonical's Ubuntu for smartphones and tablets, is sticking with upstart because, "Migration to systemd is blocked on touch (too old kernels, some unported jobs), and was not scheduled for vivid."
One change you will notice is that all applications now use local menus rather than the global menu for the application with the focus. If you really like global menu, you can still switch to it.
Another visual difference is that instead of a variation of Ubuntu orange for the background, the desktop now uses a purplish color.
4) Still using Unity 7 for the desktop
You'll see it but you won't notice that Ubuntu is using the last iteration of Unity 7 for its desktop. Canonical, Ubuntu's parent company, has been working on the more touch-friendly Unity 8 desktop using the Mir display technology for years and it's still not ready.
I think Unity and Mir have a lot of promise, but while you can run them in Ubuntu 15.04, they're still not ready for prime time. Darn it.
5) Updated applications
As usual, Ubuntu comes with all its major applications refreshed to their newest versions. These include Firefox 37.0 for the web browser and LibreOffice 18.104.22.168 for the office suite.
Taken as a whole, easily the biggest change in this latest Ubuntu update is the switch to systemd. All together this is a good, solid upgrade with many improvements. I look forward to switching over my production Ubuntu system to it by month's end.