Its the shape
The flat shape fits your back better than the other sausage-like bladders.

Well-made; easy to use
This is my first hydration bladder, so I don't have experience with others to compare with it, however it fits nicely in my Deuter internal frame pack, connecting easily to the built-in Velcro hang strip. It is easy to open, fill and seal with the top slip clip. Water flows easily through the bite valve, and no drips. I detected a slight chemically taste during the first use, but it seems to be less obvious after repeat uses. No leaks from the tough material and securely constructed seams. Cleans and dries easily due to the full width top opening. So far I have found this to be a reliable and easy-to-use hydration system.

Love It
I love it, I've had a lot of hydration packs and Deuter is the best. And really easy to clean.

Great product
This is very well made. Great quality of components. Very easy to clean. Good functionality. First class all the way. I like quality stuff at a reasonable price and this fits the bill! I am very pleased with it.

It worked, but I like my CamelBak better
Just tested mine out. I appreciated the wide opening as it was easy to clean but overall, I thought it left a little to be desired. I didn't care so much for the top clip mechanism and I don't think the bite valve system (twist then bite) is quite as easy to use as CamelBak's. Also didn't care for or need the bite valve cap. I felt like I had to go with the Source bladder because the wide velcro hanging strip in my Deuter pack didn't work with my CamelBak's hook.