Same here. I'm a paying dropbox customer, but I plan to switch in a month before my annual subscription renews. Amazon drive offers more space for only $60 USD a year.
Plus google apps offers more space than dropboxes business plan.
I tried to switch quite many times. Problems are typically: refusal to sync some files, excessive memory and CPU use (last time I tried OneDrive it used ~700MB RAM when storage was nearly empty), no LAN sync (speeds up things considerably when sharing with family/colleagues), no block-level sync (touch a small part of a 300MB file and it gets completely resynced), no Linux client.
rclone plus Amazon Cloud Drive might be an option. They do seem to have no limit when it comes to uploading data, but you can apparently run into soft caps if you try to download it all at once. Apparently Amazon has a lot of spare downstream capacity at their datacenters.
Plus google apps offers more space than dropboxes business plan.