just to let you know: I recently updated from 2.3 stable to 2.4.0~20180701105417-1 on my raspberry and rules, addons unchanged (addons updated) the performance is really impressive. Rules still take some time to compile but it seems to be faster. Load dropped considerably - from 0.95 to 0.05
Didn’t notice any problems upgrading. Justed changed the APT repo source and updated (apt update & apt upgrade).
EDIT: Changed load as I had another process running