What are few limitations of Savepoint or Transaction Control in Salesforce Apex?

Each savepoint you set counts against the governor limit for DML statements.
Static variables are not reverted during a rollback. If you try to run the trigger again, the static variables retain the values from the first run.
Each rollback counts against the governor limit for DML statements. You will receive a Runtime error if you try to rollback the database additional times.
The ID on an sObject inserted after setting a savepoint is not cleared after a rollback.