Can't get it to run in VirtualBox on an MBP.

I think qemu works better for bsds you might try that

i'm anxious to see hammer stabilize and get ported to other operating systems.

I've given a quick shot to the previous release. Hammer seems stable, after some days of moderate use. It has nice features too, but it requires a "pruner/reblocker" cron job once in a while that might impact performance on a busy machine.

I'm more curious as to how the latest release scales to multiple processors, given the additional MPSAFE advances they made.