How many tables will be there in Magento 1.8
I wouldn't worry if I were you. Many systems (Oracle's EBS e-business suite) have gazillions (a techical term meaning a large number) of tables, most of which will never be used by many customers. Any major e-commerce/ERP/ERM system will be like this. You'll find that you'll be spending 85% of your time working with just a few modules which are core to your own business - and that's as it should be.

Just as a matter of interest, what prompted you to go with Magento? You business speciality? Are you going commerical or Open Source? Did you consider other solutions Sugar CRM/Adiempere/Apache OfBiz?