> curved cuts they use a router, though they couldn't
> find out what bit they use.

A router does work, but you have to be very confident with
your tools and jig. Acrylic will shatter all over the place. I've
used a 6mm carbide flute a couple of times making cut-outs
for LCDs but didn't feel terribly comfortable doing it. You
can get 3mm flutes, although that probably wouldn't make
a lot of difference generally unless you're interested in the
internal radius of corners (that you could finish off with a
square or rat-tail file anyway)

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.