iCloud Drive
Uploading is so excruciatingly slow, even with the OS in safe mode, that I can't effectively test the service or the new features. If I'm lucky, a few hundred bytes per second. YMMV and we should make no judgement whilst things are pre-release.
I'm in the UK, south coast (City of Brighton and Hove), using
TalkTalk broadband with a fibre connection. From an adjacent computer running Kubuntu, a lazy test result (not bothering to stem the flows of traffic to/from the three or more other devices that use the same router):
http://www.thinkbroadband.com/speedtest/results.html?id=146861381831610536959 – with that 18.3 Mbps upload example, I don't imagine that my ISP is contributory to the slowness with iCloud.
Competition
A few years ago (before a merger with LaCie) I often recommended Wuala.
Things changed significantly in 2011; the recommendations ceased. Later, LaCie was acquired by Seagate and eventually,
Wuala ceased.
I do have Dropbox and Microsoft OneDrive, but I refrain from using both services so I can't make a comparison.
I sometimes test
Upthere beta on Android. Beyond the beta (reasonably soon) there'll be a web client to enjoy.