I've just read Mary Jo Foley's Fortune article on Steve Ballmer's career at Microsoft.
I've followed Microsoft (and Ballmer) since the beginning and I think it's a fair portrayal. It emphasizes what he did (and downplays some of the missteps), but there are plenty of other articles about those.
I think that Steve Ballmer did a good job at Microsoft. He took a company that was struggling to get to the next stage and he took them in interesting (and sometimes new) directions. Without Microsoft and Ballmer, the computer industry would have been a different and less intereting place. In spite of Ballmer's public persona I found him to be one of Microsoft's "grown ups," taking a company from being young and sometimes thoughtless to a more mature state.
There will be dozens of articles about Ballmer in the next few months. But his real legacy will be whom he helps choose to be Microsoft's next CEO.