[otrs] Importing data from another ticket system

Hi all... I want to switch from our current ticket system to otrs, however I do not want to lose all our old data. I'm wondering if anyone has successfully imported data from another ticket system. Is there currently any mechanism to import, say, XML files into the database? If not, then I guess I would have to write up some kind of script to manually insert the data into the database myself. I'm just looking for comments on this. Is there anything I should be careful of? Thanks, Greg