So far the experience is great. It is much faster than Juno. Main problem I had with Juno is that it is damn slow even with the updates provided later by eclipse to fix the slowness issue. But Kepler seems to have fixed all those issues properly.
Most notable improvement for me so far is the improved Eclipse Marketplace. Now we can select multiple plugins once and do the installation together. Previously we had to install plugins one-by-one. And also conflict resolution related to plugin installation had been improved. Previously when there is a conflict, eclipse only tell that installation cannot be completed, but now it says exactly which plugin causes the problem and gives option to continue installation without it.
One problem I had was that there is no official support for Scala-IDE for Kepler. But managed to find a scala-ide build from scala-ide google group. It was working fine, so until official version is available I'll be able servile with it.