From a Mary Jo Foley review; also see Microsoft Surface Laptop Review: Worth the Wait (The Verge)
"So what's my lappability rating on Surface Laptop? I'd give it a 7.5. It's more lappable than I thought it might be when I had a few moments with it at the Surface Laptop launch in early May. But its 3:2 aspect ratio and location of the batteries behind the screen still leave it a bit more top heavy than I'd like. I also find the screen a bit wobbly when poked/touched and the base a bit slippery, requiring me to hold the device in place firmly with my wrists. All that said, I'd still call this Microsoft's most lappable Surface device to date.Review: Microsoft's Surface Laptop | ZDNet
I understand not everyone wants or needs to use a laptop on her/his lap. On a flat surface, the newest Surface is well balanced, even when using touch, which is not the case with the Surface Book in my limited experience. The Surface Laptop also works with Microsoft's pens and Dial, but I didn't try it with either. I am one of the estimated 70 percent of Surface users who don't need or use a pen. I also don't often use touch, as the trackpad on this device is quite good."