Recently magento 1.5 is in available stable in market so i try this and find out some advantages and disadvantages of new magento 1.5
Magento 1.5 has some 10 important points to choose it
1) You may now export your customers and product from Magento backend with an advanced attribute filter feature.
The good old dataflow profile feature is still available.
2) Now you don’t have to edit XML files to modify order state and status as this can be done from the backend.
3) This will be very useful to customer services: you may now edit an address without having to create another order.
Be careful though: this will not recalculate order amount or shipping fees.
4) The 1.5 Magento Commerce comes with a new Magento Connect Manager Upgrade. The new version is 2.0 of the Magento Connect Manager
1) Still heavily layered and overly complicated coding style and thousands of files requires a lot of time to learn and do customizations
4) Still runs fairly slow
5) Still requires a good high end server