Excellent program, the best in its class by far. The developer is very hard working and dedicated to making this a great program. I have had very quick turnaround times on bug reports and feature requests.
AFAIK YAFU has the world's best QS implementation, and its ability to intelligently choose a factorization strategy on its own is really marvelously useful. YAFU is pretty much where it's at for integer factorization.
An excellent factoring utility by a dedicated developer.