Try installing opis and see what is causing all the lag. But about the update im enjoying it.I tried out another pack, and it worked just fine. I updated the pack, added fastcraft, turned off aroma backup (because I read that may have been the issue), and tried with a new world. None of that seems to have changed the CPU usage. It is still stuck at 250% usage.
I haven't gotten to try out the new update yet, sorry!