Can the iCloud sync progress be observed?
There are no built-in OS X tools designed explicitly for showing you iCloud synchronise information.

As of OS X 10.8.2, Apple has not made this information public. Unless Apple publish OS X Application Programmer Interfaces (APIs) to provide the information you seek, no third party will be able to accurately provide the synchronisation details.

Given this, please give Apple's iCloud team feedback; let Apple's engineers know what you want and why.

While you wait, you can track connections to Apple's iCloud servers, measure traffic flow, and disk access. These metrics will provide some insight but they will not provide expected durations or percentage complete measures.

To explore the data flow, explore the OS X's built-in tools like lsof and netstat.