I have about a half dozen packs that qualify as day packs, all but two are traditional styled packs, of the two that aren't, both are clones of Maxpedition offerings, 0ne is of a Falcon II assault pack, the other is of the Jumbo Versipack, I like how backpacks carry, but I have trouble putting them on and getting out of them because of arthritis in my shoulders, the Jumbo Versipack messenger bag is a lot easier for me to carry on most day hikes.
One backpack that I have recently purchased is showing promise, it's a Hidden Woodsman Day Ruck, it carries pretty comfortably, it's a relatively small pack at a max of 20 Lt., but I like small packs because they force you to not over pack.
The thing I like about the Hidden Woodsman Day ruck is that it's a traditional bucket styled Rucksack design yet incorporates newer Nylon and Cordura fabrics and while it doesn't look like a military pack it has a lot of molly attachment points to it, also it's 100% American made including all the materials, zippers and buckles, and completely assembled in the USA by a small basically one man shop in the good old USA.
Like all high quality gear the Hidden Woodsman day ruck is not cheap for a fairly small pack, at about $245.00 it is pricy compared to an off the shelf Ozark Trails backpack from Wally World, but considering that they are built one at a time completely by hand and sewed by hand on a conventional sewing machine by one guy, you are getting what you pay for, and that overall quality and attention to detail.
The Jumbo Versipack is surprisingly versatile when it comes to being able to carry about everything one could need for a day in the bush or on a trail hike, and it can be carried on your side or towards the middle of your back, by moving it every once in a while it makes the bag carry more comfortably over time.
