Do you restrict any features in MySQL 4.1/5.0?

Yes. To protect our shared servers we restrict the following features:

MySQL 5.0:

• Triggers will not be supported in the MySql 5.0 offering because the SUPER privilege is needed to run all triggers. A bug report was submitted to MySql AB for a privilege tables fix in later versions of MySql 5.1.
• Stored functions are not allowed, however, deterministic stored procedures/routines will be supported. For more information see Are stored procedures allowed in MySQL

MySQL 4.1 and 5.0:

• The Berkeley storage engine is no longer supported by us or MySQL AB. If you have tables which use the Berkeley storage engine you may continue to use that table, however we will not support it. We advise that all customers convert their Berkeley storage engine tables into InnoDB.