I've used EXP Autos for Joomla 1.5. With the help of the EXP team I've successfully migrated my huge car database to 1.7 (even though migration wasn't straight forward - I've been using Joomla for more than 5 years).
Support is nearly always there ready to assist.
Cons: Poor level of English from support.
Pro: Service level, willingless to support, flexibility & features of component, easy to edit code