If you have the money to spare, yes it is worth it.
It will allow for much easier and smoother sheeting. On my old 14 I upgraded to the Harkens... between the better ratchet, extra purchase, and the all around better feel it made my sailing much more enjoyable.
If you want to run any kind of rake it is almost impossible with the old seaways on the 14 but due to the lower profile of the Harkens you can. Unless you are racing long courses I would stay with your mast raked very little though.