It's difficult for a company that thrives on something as theoretical as architecture to design real gadgets that real people can use. Having said that, they have been successful with their Xbox and Kinect and they are making the attempt with their Surface. Also, a large part of the user experience on devices running their operating systems can be attributed to their design. They are not new to user facing technology design. Apple's designs are far better.
Still, while I wouldn't rule out the possibility of them being successful as a gadget designer, I would bin it as unlikely. Operating systems and end-use gadgets are two different mindsets. The consumers expectations of what a device should do for them has changed in part due to Apple's introduction of game-changing device options. It will be difficult for MS to adapt to this new way.