As has been noted, AcceleratedX exists for netbsd.  So I downloaded their
demo and ran some of the std benchmarks on my netbsd machine, a 386-25
with 8 megs of ram and an ATI Graphics Ultra Plus card (2 meg DRAM/ISA).

The end result is that Xfree86 came out faster on this machine (50K xstones
to 40K xstones) than Accelerated-X from x-inside.  However, the massive 
number of video cards supported by Accelerated-X may cause me to buy the
commercial product none-the-less.

Accelerated-X
TOTAL    176452 lineStones
TOTAL     23282 fillStones
TOTAL     17934 blitStones
TOTAL   1219134 arcStones
TOTAL    107593 textStones
TOTAL     42483 complexStones
TOTAL     41028 xStones

Xfree86 
TOTAL    136661 lineStones
TOTAL     33919 fillStones
TOTAL     28535 blitStones
TOTAL    921287 arcStones
TOTAL     67031 textStones
TOTAL     49215 complexStones
TOTAL     50118 xStones