So after getting home and spending about 20min with the new core, here's what happened for me..
Core loads and proceeded to boot my default config into Workbench, but halted here:
So, cold reboot, and boots into WB fine... In fact it seemed quicker and snappier than before.. so i tried running some demos, listening some mods, and using some software, and no problems, everything perfect, played around for about 15min.
I then decided to cold reboot again to make sure the disk boot problem didn't recur, it did not thankfully, so decided to try some more whdload demos, I tried to Mind Riot by Andromeda, launch to black screen and immediate crash to guru med. Had to reboot again, normal ctrl-A-A not working, had to cold reboot.
So I tried Mind Riot again, this time worked no problems.
Inconsistent behaviour, and while it does seem fractionaly quicker, for me anyway, it just seems less stable, unpredictable errors and crashes here and there.