For me it is worth it. Based on the fact that I have the upgrades available, I have the financial means to do so, and I enjoy having the newest iteration of the iphone. I am coming from the 5, so perhaps the 'upgrade' won't be substantial, but I will welcome any improvements to speed, camera, storage amounts, etc.
From a different perspective, if the difference between a reduced-priced 5 and the new 5S is say, $100.....then you need to look at whatever the new features are and ask yourself....would you pay $100 to have those new features on your phone? Especially if you are one who keeps their device for the full 2 year contract. If so, then there is your answer. You can also factor in that perhaps you would recoup some of that $100 difference down the road when you go to trade-in or resell.
And a final perspective might be...are you using a valuable upgrade to get this new device? If so, would either the 5 or the 5S be enough to entice you from waiting to see what the iphone 6 will offer? Of course, if we always wait for the next best thing around the corner.....then we would never commit to anything. But, it's a valid question. Are you in the position to bypass both the 5 and the 5S to see if the 6 changes the game?
Best of luck with your decision. Fortunately, you are getting a great device no matter what you decide.