I'm trying to install / compile ROS on Unbutu 14.10, but it seems it's not supported?
Correct, at least not yet. See REP-003 for the list of supported Ubuntu platforms. Indigo is supported on Ubuntu Trusty. ROS Jade will support both Ubuntu Trusty (14.04) and Ubuntu Utopic (14.10) (and Vivid).
I wonder how different it is from 14.04?
Different enough to only be considered for Utopic.
rosinstall_generator desktop_full --rosdistro utopic --deps --wet-only --tar > utopic-desktop-full-wet.rosinstall
The argument is called rosdistro, but you are supplying it with the name of an Ubuntu distribution. That won't work.
Decide for yourself with ROS distribution you want to install, and replace utopic with the codename of the ROS distribution (ie: groovy, hydro, indigo, or jade). Note that only Jade is 'designed' to work on Ubuntu Utopic, the others are too old. Jade has not been released though, so it may not be complete.
I wonder if 14.10 will be supported soon, [..]
See my earlier comment about ROS Jade.
[..] if there is an easy way to make this work?
A from-source install is an option, but I'm not sure whether that can be considered easy. If Indigo's dependencies on Utopic are similar enough, things may work.