Re: Pointy Plaster Ceiling Removal *with pic*
That's just nasty. :-)
Personally, I'd try scraping it first with something like my handy 5-in-1 painter's tool (maybe a hammer too). No promises, but you might be able to get it down to something closer to smooth, especially if it was done with mud (aka- joint compound). Then make the choice to sand, or skim. Be careful not to dig to deep when scraping. (Ever use a wood chisel and mallet?)
Even if you choose to rock over it, you might still want to knock down those high points. Tearing it out may be the better long term solution as it doesn't add weight to the ceiling, but it can be a mess if there's insulation above.
"I think that's gonna leave a mark."