I read a lot of reviews before I purchased my GUTR, and I'm glad I bought it. I had a lot of trouble with sweat dripping inside my sunglasses on my cycling rides, especially since I love to ride in very hot weather. While you're still going to sweat - even underneath the band - it cut down my problems immensely. I'm reviewing this after using it on six very hot rides.
I'd like to add a few notes:
1. Make sure it is secured snugly, but not too tight. I had a splitting headache and I stopped, loosened the band a bit, and the headache went away.
2. Make sure that the Velcro is secured. I didn't secure it much and the band almost fell off. That's my fault, and I won't make that mistake again.
3. I've been reading reviews from people who said the band had a bad odor - it doesn't at all - make sure you rinse it in water after each use. I think the people who made that comment need to examine their own foul hygiene practices.