I have a love-hate relationship with Microsoft.  I love what Windows/IE did to open up the world of computing to non-geeks.  No matter how much we may hate MS, we have to recognize that the home computer/internet explosion of the late 90s was directly attributable to Microsoft.
On the other hand, there are many reasons to despise MS.  I refer you to 
www.fuckmicrosoft.com if you want to know all of them.  For me, the two primary reasons are bloat-ware and the privacy issues.  Secondary issues are their business practices and the way they have monopolized the industry with regard to home/office computing.  They created a vicious cycle:  they created for themselves a dominant position in the industry by making the easiest (for non compusavy users) OS.  As a result, most software is designed to work (first and foremost) on their OS's, which leads to a more dominant position for them, which leads to more software being written primarily for windows, etc, etc.
I do admire Bill Gates for one thing, though.  I dont think anyone can deny that he is the epitome of the American capitalist success story.  I have no doubt that he and his company will be studied by generations and generations of business students.  He is, after all, THE most successful entreprenuer of all time.