This little bladder pack is perfect size for training rides where you just want to go out, get your heart-rate up and get the job done. Small zipper holds a gel or two, keys and a phone. I like the mesh straps as they help to keep the shoulders from heating up.
I will echo the lack of a chest-strap complaint. I think that regardless of the size of the pack a sternum strap is necessary. It is such a simple addition but it provides the user with increased pack stability.
That being said, if you go to your local craft store you can get buckles, and some webbing and make your own inexpensively and quickly. I think that a few companies may also sell pre-made units.
Also, the bladder is essentially suck inside the pack. There is an intricate folded panel system holding the bladder in, thus making it difficult to remove for drying purposes. The saving grace of that issue is that the widemouth design allows you to towel dry the inside.
Aside from those small little issues, this is a great stripped-down pack.