I noticed this from Syl:
"No. But Kaladin, you have to understand. With this sword, someone can do what you can, but without the ... check a spren requires." She touched it, then shivered visibly, her form blurring for a second. "This sword gave the assassin power to use lashings, but it also fed upon his Stormlight. A person who uses this will need far, far more Light than you will. Dangerous levels of it."
page 1059
It seems that the forums have focused on the difference in efficiency in honorblade vs Nahel bond but that last sentence has stuck with me since me since i read it. I don't seem to remember anything referencing Stormlight being dangerous anywhere else.
The only other use that seems to effect the user negatively is the soulcasters that Adolin sees that have stonelike skin but i feel we don't know enough to make a connection there. That could be from the fabrials or the prolonged use. Either way its creepy.
Any thoughts on this?