I just wanted to ask if anyone had recommendations for a good backpack that hits a good middle point between being low-profile, but still being comfortable and able to carry a good bit of stuff.

Last year I was rocking around with a nice drawstring bag, but after enough time, the strings started to dig into my shoulders. This year, I'm considering a Timbuk2 Swig backpack, but I figured before pulling the trigger, I'd consult all you wonderful people. Plus, it may be a good resource for folks leading up to Gen Con.

I never liked those drawstring bags.  They look like they are so bad for your back.  I use an old Wolf Creek backpack I’ve had for 20 years.  The real trick is to not overload your bag with stuff you really don’t need.

Dragon Egg by Direct Action. Cheap backpacks = pain. 

I like the Think Geek Bag of Holding (Con-Survival version), it is a messenger bag but good design and size.  Have not had any issues carrying my stuff.  

I also use the Think Geek Bag of Holding.   I have two bad shoulders, and this has been the best solution for me.

The Timbuk 2 Swig looks like it will hold more stuff, so that might be the better option for you.  I know with the Bag of Holding that a regular sized board game box takes most of the space.  Two would be right out.

I've been looking at the Bag of Holding, but I've never used a messenger bag, so I'm unsure of how well it would work for me. For the most part, I consolidate my board game purchases to one part of the day so that I don't have to lug a bunch around all day, so the backpack/bag will be for smaller stuff/essentials

My wife unfortunately has to walk with a walker due to back issues.  We usually put most of our stuff on that.

No specific bags to recommend, but if you're planning on carrying a lot of stuff, especially heavy stuff, something with cinch straps to stop the contents from moving & pull it close to your back makes things more comfortable. And reduces the amount of bag sticking out behind you.

If you're also traveling a fair way, and you don't mind looking like a lost hiker, a waist to get the load off your shoulders should make things more comfortable at the end of the day.

Get something that is comfortable. You will be carrying it all day. 

I ended up getting one of the GenCon messenger bags, carried everything for the 3 of us without any trouble. Plus it was maneuverable in the dealer hall and never got caught up in the crowd. 

I find messenger or briefcase bags are best in general.  I have softside briefcase bag that holds a lot of stuff, but doesn't collapse much if it's empty, so for days when I don't have to tote much I use the messenger bag (as it is light and compact).

The main advantage of these over backpacks? 
You can carry it on the shoulder or off.  There were plenty of times where it was easier to unsling the bag and just carry it by the handles for a bit.  Whether that was because I was maneuvering thru a crowd (and could hold the bag in front of me as I squeezed) or because the shoulder was tired but the arm was still fresh (usually hours after purchasing something I had not had a chance to drop off at the room).
You can also fit them under your chair at the game table with the strap draped across the seat, in case you are concerned about theft.

General rule is don't try to cheap it on backpacks, and more importantly, shoes.  Spend the extra money, your back (and legs) will thank you.

I run a camelback backpack... because I like to stay hydrated and it's an all in one container for it
 

just don't bring rolling luggage to the convention center floor... please.

The GORUCK GR1. The first and last ruck you'll ever need.

I carry an Oakley back pack and love it!!!!!   It is called the kitchen sink.  It is a bit pricey but the best $ I ever spent!!!   Yes the name is actually "The Kitchen Sink"

Just push everything around in a shopping cart.  Makes sure one of the wheels is slightly broken so it veers to one side or another.

I'm a huge fan of the Samsonite Xenon 3.0 Small Backpack Business. I carried it with no problems all last GenCon and had enough room for my gaming binder, snacks, dice, and dice tray!