It's worth it's weight in gold! My hydration bladder carries 3 liters of water and I find it much more convenient than carrying nalgene bottles alone. I also tend to drink more as it is easier to get to than having to pull out a nalgene. I use it for hiking and mountain biking and would be lost without it. I currently use the Camelbak brand, but have also used the cheap systems that WalMart stocks for $9. I prefer the spout on my Camelbak over the cheaper bag as it can be easily opened and closed to stop drips. I transfer my hydration system over to whatever backpack, or daypack I am using for the day. On hiking trips we always bring a filter as well and can easily fill up our hydration bladders along the way if need be.