I have put this as a new post rather than add it to the existing iCloud sync broken thread because I suspect the same tricks may apply to Dropbox syncing, and I didn't want Dropbox syncers to miss it.
By a lot of trial and error, I seem to have found some kind of way for making iCloud syncing work with ver 4.3 consistently.
The essential elements are:
Have "File Sharing" turned on in the sync settings. ( I only want iCloud sync, but having File Sharing set to off seems to be the cause of hangs and continuous cogs)
Don't touch the "sync now" button. Unlike in 4.2.7, it doesn't respond and trying it seems to prevent subsequent syncing.
With the above I seem to have changes made on the iOS device auto synced to my Mac and vice versa.
If it stops working (like after I tried pressing "sync now") then quitting 1P by double clicking the home button and sliding the 1P screen up, and restarting 1P seems to get it working again.
NB in getting to the above state I did a lot of things like turning iCloud Docs off and on and uninstalling 1P completely. These may or may not have been necessary.