Hi folks,
as mentioned above, I didn't have problems syncing the preferences to a second machine - in my setup simply enabling the sync feature on one single Mac reset all my settings which should have been synced and I was unable to permanently change stuff from that point on.
So I tried again with v2.0 build 131 - but to no avail.
As it turned out, the problem actually was a Dropbox problem, but nothing that could have been changed by waiting for a complete dropbox sync: I thought it would be a good idea to use a subfolder of the Dropbox "Apps" folder for keeping the Alfred prefs -