Its basically a very old National Simple Switcher IC with some current and voltage feedback wrapped around it. If you want to charge batteries, etc, at medium currents, its probably ok generally- I would find a place to put a diode, probably after the inductor inside the loop. Ripple and noise won't be very good. Transient load response won't be great and I can't imagine it might oscillate at certain V and I's. You can buy a pretty competently designed chinese switcher PSU in a box with meters, etc for about $50.
The problem with making a variable buck like this is that the inductor value or the current limits really needs to change to cover such a wide range of I's and V's. The buck converter is a fixed frequency type with cycle current limiting, at reasonable loads, it will find a PWM value that will work well but if it kind of falls apart at lighter loads and will get into a pulse skipping at lower frequencies where you'll get lots of ripple.
Its ok for the garage but its far from a lab supply.