This question has been answered by mdsdesign. See the first response.
Updating to 1.2.1 shouldn't be a problem, unless you have snippets / modules that use MYSQL instead of MYSQLi
If you run into that problem, you can change the config.inc.php to use MYSQL, but thats only a temp solution
The simple answer to that is NO
All the snippets that come as default work, so I suggest taking a look at what you have installed and whats in the download
If you have stuff thats not in the download, they might have problems.
More info about the MYSQL change can be found here and here