After you install the Assest Tracking module make sure you set the customized record numbering in vtiger settings before using else, else it won't accept any asset tag numbers.
Settings > Customize Record Numbering
Pick 'Assets' from the 'Select Module' drop-down list.
Thanks for the compliments. I have given it some thought, and I will work on getting a generic demo working so people can take it for a real test drive. If enough people like it I'll put the work into getting it good saleable/installable shape.