Sync up seems to work effortlessly but I did notice that when I had to exchange phones that it wiped out my photos on Skydrive...didn't realize that would happen as I've never had anything delete from Dropbox unless I intentionally went in and deleted it.
I've had the SkyDrive for a few years and am grandfathered in to the 25GB of free space. I haven't ever had any sync issues and love the auto sync when you take photos so I can easily locate them online and share them out. IMO the SkyDrive has been one of those little known offerings that provide a great benefit and as usual MS has done a poor job of marketing it.
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.