The usual forks are taking part in the first beta, including Kubuntu, Lubuntu, Ubuntu Kylin, Xubuntu, and Ubuntu GNOME. As always, the mainline Ubuntu release does not participate in these early testing builds.
Ubuntu GNOME 14.10 Beta 1 includes, as with the previous alpha release, GNOME Shell 3.12 and the addition of the Weather and Maps apps installed by default.
Kubuntu 14.10 Beta 1 includes KDE Platform 4.14, released just over a week ago. Testing for the next generation Plasma 5 desktop is still ongoing in a separate image.
Xubuntu sat out the alphas, but Xubuntu 14.10 Beta 1 is here with theming support for GTK 3.12, keyboard backlight controls through the Xfce power manager, and a raft of Xfce updates you can find in the official announcement.
Beta 1 images are also available for Lubuntu, Ubuntu Kylin, and supported Ubuntu Cloud platforms.
With the first beta of Ubuntu 14.10 here, the next release will be the final beta tentatively due on September 25, including the first beta release of mainline Ubuntu. A release candidate should drop on October 16, just ahead of the final release of Ubuntu 14.10 on October 23.