The Financial Times had lunch with Ahtisaari. It didn't come cheap (€284.45 for two people), but it gives a nice view in the way Ahtisaari thinks.
Ahtisaari (1937) joined the Ministry for Foreign Affairs of Finland at the age of 28. Before he had been involved in development aid. He made career and became Finland ambassador in Tanzania in 1973. Part of this job was keeping contact with liberation movements in southern Africa. This resulted in a UN job that made him responsible for Namibia in 1976. He stayed involved until Namibia's independence in 1989. Ahtisaari sees this as his greatest accomplishment and according to the article the Namibia agreement served as a model for South Africa later on.
Ahtisaari has tried to apply the lessons he learned from Namibia elsewhere. The lesson that he explicitly mentions is "I don’t think you can get any solution without the Americans, in most of the conflicts". I beg to disagree. Sure, the US can spoil negotiations: for years it supported Apartheid in its battle against communism and recently it torpedoed negotiations between Israel and Syria. But the record of the US in positively influencing peace is rather poor. About every other year it has some peace initiative in the Middle East, yet the only time it achieved something were the Camp David agreements in 1978. Usually the US is too pro-Israelian to achieve anything, but this time it was strongly motivated to get Egypt in its sphere of influence and outside Russia's.
Namibia happened to be another case were the US position helped instead of obstructed. The US had become convinced that Apartheid was no longer defensible. Yet it was afraid of the pro-communist leanings of the liberation movements. So it pressed for a solution that stressed democracy and guaranteed free markets. This position fitted with that of Namibia's white rulers as it protected them against nationalizations, land redistribution and other redistributive policies. It was the kind of chance that would hurt the Whites the least and so was most acceptable to them.
Kosovo was more like the Middle East. Lacking strong interests for itself the US had adopted the Albanian position as its own. This bound it to such unfortunately strict ideas as "no border changes". By adopting this as his own position Ahtisaari made it very difficult for himself to find a solution.
Another point that Ahtisaari doesn't mention is "principles". In the case of Namibia the principle that Apartheid was no longer acceptable played a strong role. I suppose that Ahtisaari derived from this the idea that the Kosovo negotiations needed a principle too. This became the idea that Serbs should no longer rule over Kosovo. I think that this was a major blunder as it declared the Albanian bad experiences with Serb rule and their wish not to repeat it as fundamentally different from the Serb bad experiences with Albanian rule and their wishes in this regard.
A third lesson may have been that you can solve everything by just having the right laws. The Whites in Namibia were happy without much minority protection, so why shouldn't the Serbs be able to do the same. This ignored the fact while the Whites in Namibia negotiated from a position of power the Serbs negotiated as a persecuted minority, half of which lived in exile. Being in a much worse position they need much stronger guarantees that this position will be improved.
Finally there is Ahtisaari modus operandi. He is a typical networker whose strength is that he knows so many people who can help him to solve a problem. However, once seeing him in a lecture gave me the impression that he is not very fond of details. I couldn't find a sign that he has any idea what the situation on the ground in Kosovo looks like.
Ahtisaari has been asked to mediate in the Croatian-Slovenian border conflict. He would be part of a troika that might also include Badinter.