The investors claim that Gates as chairman blocks the adoption of new strategies, and similarly that he will tie the hands of whoever is chosen to replace Steve Ballmer as CEO. Gates' role on the committee to find Ballmer's replacement is cited as evidence for this.
The Microsoft board has already said that Ballmer's Devices and Services initiative will continue under the new CEO.
There is also concern that Gates is more interested in his charitable work and that his influence is more significant than his shareholding should imply. Gates is still the largest single shareholder, owning about 4.5 percent of the company, but he is set to reduce his stake to zero by 2018.
It's hard to know what "new strategies" Gates might be blocking. Microsoft, lest one forget, is a company that became powerful on the back of selling perpetual software licenses to hardware companies, enterprises, and end users.
Get rid of him!