The key differences you will notice are
1. slightly faster 'hard drive' performance
2. Haswell chip will be much faster over C2D for applications that require CPU tasks. Don't expect any difference for web browsing, typing in Word/Excel/Pages.
3. Video card is much improved
4. Quieter/less heat
5. Backlit keyboard (why did Apple remove this???)
Depending on your tasks I would say yes, but if you are just surfing, typing, XL, the odd video then i would say no, not worth it.