This article is from the Go FAQ, by Morten PAHLE firstname.lastname@example.org with numerous contributions by others.
As already explained, computers make weak opponents. Since they cannot
learn, they also make boring opponents, as they make the same mistakes
over and over again. Of course it can be fun to beat a computer which
takes a 9-stone handicap, but the methods used to beat it are unlikely
to work against human players, and may even give you bad habits.
However, computer programs play each other in various tournaments and
can be ranked by their relative strengths.
Here is an excerpt from <http://www.smart-games.com/worldcompgo.html>,
edited by David FOTLAND.
It gives an indication of the 'average placement in an international
competition', based on recent results in international computer Go
Top ten Go playing computer programs (Last updated September 1999):
Author Program Score M Reiss Go4++ 2.3 Chen ZhiXing Handtalk 2.9 Ryuichi Kawa Haruka 3.0 KCC team KCC IGO 4.0 D Fotland Many Faces 4.3 Lei Xiuyu Wulu 4.7 Ken Chen Go Intellect 6.2 A Knoepfle Modgo 6.8 Yong Goo Park Fun Go 7.2 J Kraszek Star of Poland 7.6