Dropbox for me too.
- LAN Sync is a must for me (Google Drive doesn't have it)
- Flawless
- I currently have 15Gb of storage for free (referrals, dropquest, camera upload, ...)
- Google Drive offers office files editing on the web but it is limited to G.Drive files so it's pointless for me as my files are native Word or Excel
- Dropbox Web interface is way better IMO
- Sharing is simplier
- Been a long time Dropbox fan
- Partial sync (selected folder) (Google Drive has it too)
- Way more popular API (Lot of my iOS apps use Dropbox)
- Dropbox Mobile App is better than Google's ones
On the minus side, it is pricier than Google Drive but I'm still having enough free space without paying. However, if needed, I'll upgrade to Pro 100Gb ($99 a year = $8 a month compared to Google's $5 a month).
I also briefly tried Box.net (I have the free 50Gb) and Skydrive (Free 25Gb) and even subscribed to Sugarsync about 3 years ago but Dropbox beats them all IMO.