I received this one yesterday. It's $51 on amazon, but ebags has better pics.

High Sierra Riptide 25 Backpack - eBags.com

What I carry:
Complete change of clothes for business casual (jeans would obviously take up more room than dress slacks or khakis)
Towel
I keep my shoes at work, but they would fit if I needed them to.

All shower needs are kept at my desk.

I used it this morning and it's awesome. Plenty of room for everything you need for your commute. My first thought was "that's too small", but as I started stowing my usual stuff I realized that it was going to fit perfect. There are a handful of interior pockets and a nice little pocket on the very top that would be nice if you were carrying a lunch and wanted to get to it without unloading the pack to find it.

Now, there are some down sides, but those don't affect my needs. It doesn't have a dedicated laptop sleeve and it's not waterproof. What it does offer is extra storage on the outside of the pack. The "helmet" flap can easily handle a pair of shoes or a towel if you have the pack extra full. And though the description doesn't mention them, there are a couple short "sleeping bag" straps that could hold a towel, jacket or rainfly. There are a couple "D" loops on the "helmet" flap and it has a strap for an extra rear tail light that's position to be seen when you're riding.

The other feature that I think is awesome are the zippered pockets on the waist straps. They're big enough for my HTC One phone, keys and/or a wallet. Having access to those things without unstrapping the pack is a big deal to me. Perfect for that quick Strava shut off or in my case, I need a key fob to get in my building. I don't need to dig around the pack. I can just hold the backpack up to the sensor by the door. There is also a key hanger and what looks to be a sunglass pocket on the inside.

It comes with a 2 liter hydration bladder, but I take that out for bike commuting. I'd put it back in if the pack were being used on a hike or a family day at 'insert your favorite family activity here.' The only other minor negative is it doesn't have external water bottle pockets. Not a big deal because of the bladder, but if you had to have a bottle with you, it would stow within the external "helmet" flap easily.

Now the important stuff. The back ventilation system seems to work well. It's basically a glorified metal coat hanger that lifts the load off your back. This allows air flow across your back. This morning I wore a jacket so it was tough getting a good feel for how well it worked. I'll know more after my ride home this evening. Also, the packs straps are very versatile. I'm 6'-3" and can adjust them to ride high for cycling or low enough to get the load on my hips for hiking or walking. Very comfortable, light-weight pack.

Basically, I put up with my kids school backpack for 3 months waiting to find this pack at the amazon price. I'd recommend it to anyone needing a versatile daypack or commuter backpack at an excellent price.

My lunches need to go in the main compartment of my backpacks, how much do you eat for lunch?

HA!! I typically don't pack my lunch, but that compartment is about 8" deep and could handle a couple sandwiches and a bag of chips easily. it would also be a good spot for fuel goo's and bars if you were carrying the pack for a century+ ride.

Great looking bag, but after using my wife's old Bivouac I decided I prefer something a bit "one compartment" since I usually package things in large containers/bags and don't carry a laptop. I am eyeballing the Sealline Urban backpack, might get it this weekend.

But the OPs bag may not be a bad idea for good weather, non-gear heavy commutes.