As it is basically a Pyrex tube shaped to replace the stock rubber tubing in the cooling system, I'd be surprised if there were performance changes.
I'd say it is just for looks:
The coolant flows through a clear tube, so you can see it.
The LEDs let there be neat lighting and make the flowing coolant look even more interesting.
The dye is there to change/mess w/ the color of the coolant.
As for "worth it" . . . that is up to each.
At first, I thought it was pretty stupid to be honest. But, having seen a number in action, they look MUCH better than U would have thought and may (one day and w/ a heck-of-a-deal) get one myself.
Oh, and here is the Killerglass site:
http://www.killerglass.com/One potential "performance advantage" . . . being able to visually see your coolant, in action, to check on issues w/ the cooling system . . .
