I saw someone at the gym and I got super excited about it and purchased one that day online.  I was getting sick of digging through my duffel bag and trying to find things in it and I thought that an open vertical bag would be great.  In theory, it is a great idea, but in practice this thing is too damn small.

I can fit:
- 1 pair of gym shoes
- 1 set of shower shoes
- 1 tracksuit for my drive home
- 3 pairs of shorts/shirts/socks/briefs
-  Toiletries (toothbrush, toothpaste, razor, 2 servings whey powder, small deodorant, small foot powder)

I then have to carry my water and protein shake bottles on carabiners on the outside of the bag.

Okay, that's less than I want but still acceptable for what I take *to* the gym.  However, I usually stop off at the gym on my way home so I have my work clothes, plus my sweaty gym clothes to deal with.  This means that on the way home I put my work clothes and shoes in the bag which are much bulkier than my shirt/shorts/tracksuit.  So I have to cram my work clothes AND carry sweaty clothes in a mesh bag on the outside.

So basically, I can now carry less with this bag than my previous normal duffel even attaching much of it to the outside...what's the point.

Now, this is my personal experience, maybe it works better for you, but I would encourage you to take a look at the dimension and plan out your space needs.  For you, it may work out just fine.  For me, it's barely big enough just to carry what I know I need, but way to small to carry what I would really prefer.