There's a lot written about Ballmer's successes and failures and most focus on the tangibles - Like growing revenues by x and profits by Y and such and such product bombing or taking off.
IMHO his legacy though, is the culture he leaves behind. Its an intensely competitive internal culture that has
- employees jousting with each other in the rankings game
- pressure across the board for businesses and individuals to deliver "results" in time for each annual and half year review which limited experiments and blue sky endeavors.
- over the top status mails and visibility exercises to preserve and extends one's influence
Everything else is a symptom of that - products that are kinda incomplete, or only incrementally better than the previous ones because it insanely hard to get everyone on board and ship truly game changing products in a manner that fit into the appraisal cycles.
Note the incremental approach is extremely good for more risk averse sectors like enterprise software but not really for the wild west of consumer technologies.