1. One of the most robust open source eCommerce solution in PHP
  2. Its promoted by eBay so will have a pretty long life
  3. Magento is highly scalable
  4. Magento is modular so modules can be easily added or removed
  5. Use of EAV allows it to use with endless attributes
  6. Different product type supported: Simple, Configurable, Bundle, Virtual & Downloadable
  7. Out of box sales promotion rules
  8. Bulk data import/export is easily possible
  9. Allows multi store setup
  10. Supports multi language
  11. Supports multiple currencies
  12. Is SEO friendly
  13. Has many payment gateways integrated
  14. Many shipping solution available
  15. Cache concept makes it fast
  16. FPC concept of enterprise just makes website fly
  17. Is very secure
  18. Active community
  19. Lots of add-ons available to add additional feature
  20. One page checkout
  21. Layered navigation