Just the right size for the handful of things I take with me when I leave the house. I use the front slash pocket for my keys, and the main compartment is large enough for my phone, extra glasses, wallet, regular length pens, etc. with room to spare. I've also got a mini ghost whale pouch attached inside the main pocket ring for small items like earbuds, chapstick, and aspirin that might otherwise settle to the bottom of the bag.
The stock strap is my only real complaint, as it tends to ride up on my neck quickly, but it's detachable so I'll probably end up swapping it for something wider at some point.
I tried a couple other small waist packs/sling bags before this, and the cubelet has been the most practical to use by far. I was hesitant at first about wearing something that would give off "purse" vibes, but screw it, I want to take this thing everywhere with me now, it's that handy.