I've had a great experience with it so far. I don't usually use it for large audio and video files, but I do have a ton of very large PDFs (multiple GBs in size) that never take more than a minute or so to upload. Whenever I've used it to store the random larger file (like a few home movies), those haven't taken long either to upload. In my experience the upload works just as well as (if not sometimes better than) what I experienced with Dropbox. I was already paying for increased iCloud storage for iOS backups and Photos, and realized it didn't make sense for me to pay for Dropbox when I was already paying for plenty of cloud storage for my needs from Apple. Only thing I wish it had would be selective sync for those of us who store more in the cloud than our computers can hold, but I personally haven't run into really needing this yet, and prefer to have all that stuff stored locally on my Mac anyway so it can back up to Time Machine. Hopefully they'll add that in a future release though.