I use what I consider the sweet spot of iCloud services: Calendar and contact syncing and iPhone backup. In each case, the huge convenience and timesaving that comes from using the service outweighs the occasional (and by now quite rare) frustration when it doesn’t work.
That seems to be the trend among Mac power users (see also the comments on this post).
In my experience, iCloud services are good when it comes to PIM (personal information data) data. Contacts and calendars are stable and robust. Email is OK, certainly Gmail is more flexible, but for years I haven’t needed anything more powerful.
Cloud sync/storage and complex note taking is still something that other companies are doing better.