My long beloved Matador Beast 28 is slowly dying, with a rip slowly working its way around the waist belt. My big problem with the Matador Beast was always that the side pockets were nearly worthless, at most storing a Zojirushi thermal flask that's not very big. The camel's back broke when the thermal flask started falling out of the backpack while riding.
I decided to try the Savu 5 lumbar pack when Osprey started selling them at $35. It has 2 water bottle holders, and one big central pouch. Actually riding with it, it works for commutes or even road rides of 16 miles or longer. But if you actually load up with two water bottles and tackle steep climbs with it you quickly feel lower back pain, so it's actually not so good for actual mountain biking --- I'd stick with water bottle cages.
What it proved to be surprisingly great at though is the commute --- I can squeeze in a backpacking towel, a change of clothes, badge, keys, and a cap for commuting. The side pockets can hold my headphones and the phone proper can go into a handlebar bag to keep myself from texting and riding. It's also great for day hikes, since the water bottle holders firmly accept almost any type of water bottles and hold it firmly. It won't carry quite enough for a day long hike with the family (you'll inevitably need to carry other people's lunches and jackets if you're a dad), but for short 2-4 mile hikes you'll easily have enough water for the family and a few snacks.
It's also generally good for taking kids to birthday parties and stuff like that --- the main pouch has enough room for a kindle paperwhite, so you can entertain yourself.
I thought about returning it, but Boen decided that he likes it more than his camelbak, so I'll be keeping it.