SkyDrive is awesome. I've been a power user of it for a couple years and the recent upgrades have only made it better. Between my desktop, laptop, iPhone, iPad and Lumia, all my important files are there, and I don't max it out like I did with Dropbox.
As far as the marketing, I don't think Dropbox did much, but they had the tech sites and blogs slobbering all over them, which obviously helped. Hopefully the good word of mouth will help SkyDrive.