I love it personally, although it doesn't get as much use as my S that I throw around everywhere daily
+If you want durability it's just about the best you can get, you're gonna have a hard time fucking anything up unless you go at it with trauma shears.
+Can expand or compress it down over a very wide range of volume, even if it's mostly empty you can still tighten everything down so that nothing is flopping around loose
+Decently waterproof, some water will get in through stitching if you don't have it covered but the cloth itself has a nice waterproof lining on the inside
+Fits me very comfortably even though I'm 6'4 after a while figuring out all the adjustments. I've heard the M is a bit short if you're tall, but the L seems fine
+Lots of room on the straps for attaching all kind of shit to the sides if you have stuff you want to carry externally
=Very simple internal organization, you'll have to organize your shit without babysitting but also have no space/weight wasted on dividers and pockets and shit that always end up being the wrong size for the things you are packing. The main compartment has a drawstring divider to the bottom portion with the zipper, there's a thin pouch for the frame that you can stuff a bladder in, and there's a zippered pocket on the inside of the top but that's all the compartments you get.
=No bottle holders on the side like the XL has, but I just use a bladder anyway and you get more space for attaching stuff to webbing
-Adjusting all the straps to tighten things down and tidying everything up when you need to expand or contract it takes a fair amount of time, but at least everything stays tidy once you have it set up unlike packs with elastic drawstring type compression.
Most of that applies to all the savotta packs, pretty much #1 way to go if you want something simple and durable as possible, but there's probably better options if you want something super lightweight or with more tactical high speed low drag features.