Kodi 15 (Isengard) is currently "alpha" and there is likely to be a lot of activity in the coming weeks. There will be breakage.
Many of the newclock4 commits that have been tested over the past few months are now in helix_rbp_backports and should appear in official OpenELEC builds, so if you favour stability then stick with the official builds.
I will continue with periodic build releases based on master and whatever popcornmix throws our way. Fingers crossed the generally pretty good review procedures and change management will keep problems to a minimum. Your continued feedback and testing is appreciated.