Roland System 100m

>In general, is it OK to run Japanese models on US current?  If
>no, please make the caveats mild, as I'm already slightly stressed about this

In general, yes it is OK. I have a japanese 100m (and several other 
japanese synths) and have been running them on 110V for years. The 
internal regulator merely has to dissipate slightly more power, but 
not enough to warrant concern. But don't try this with 220V.