As a Summit Hut employee since the early 2000s I have had the chance to use and abuse a number of packs from a variety of different brands. While no pack is going to work for every activity/situation my favorite all around pack has become the Imlay Canyon Gear Kolob. Imlay Canyon gear is based in Southern Utah and is run by avid canyoneer and canyon guide Tom Jones (check out his online canyon guide and Zion Canyoneering book) - these packs have been designed specifically for canyoneering, but the features make it a great pack for general use.
Why do I love it?
Durability: PVC panels protect the sides and bottom of the pack and other external areas are 1000 denier cordura. Until this pack I never had a pack that lasted more than 2 years (often developing huge holes it the bottom of the pack) - my packs has some wear but is going strong after 5 years!
(Deceptively) Simple, (highly) Effective Suspension: I was initially suspicious about such a simple looking system - but I have to say that this pack carries really well! The combination of aluminum tubing, plastics sheet and closed cell foam turns out to be incredibly effective at transferring weight to the simple but effective hip belt.
Bottom Cut: The squared off bottom you will find on some larger packs tends to 'catch' as you try to scoot off a ledge and can be awkward when scrambling. The angled cut of the bottom of the Kolob prevents the 'catching' - a great detail when off-trail and when scrambling.
Canyoneering Details: If you have gone for a swim with your pack you will know that most packs hold water just as well as they hold your gear - the Kolob has mesh behind most areas of the pack body that allows the pack to drain very quickly (key in a wet canyon). Rack strap on the inside to keep your gear easy to get to. The foam back panel comes out and unfolds - nice detail in an unexpected bivy. Quick release shoulder strap buckles - a great just-in-case feature to make it easier to get out of the pack in an awkward situation.
The Kolob is not an ultra-light pack, comes in only one size and is a on the large size for a day hike (if you love the idea of the Kolob but it is too big check out the Imlay Canyon gear Spry) - but for me it fits great and it has become my most used pack because it is incredibly durable, carries great and has enough size to swallow technical gear (or your friend's lunch) but is small enough not to get in the way while scrambling off trail.