Yes, great program: I used it to make a mosaic picture containing the maximum of 200 x 200 = 40.000 pics in it.
However, on my MacBook Pro as well on my PowerMac G5 Dual it stalls after a while, in the sense that nothing works any more, so you better make a lot of savings in between, just in case, as the program continues to look for better options even though it has found all pictures.
Good luck.