How good are these cheap frame repair kits?

Has anyone ever used one of these portable hydraulic frame pumps on their cars? And are they any good?

Don't know that specific brand but we call it a  portapower. I have used them many times. A very handy tool. 

Back in the day they were used to align twin I-beam and I-beam trucks.

when you need "all of it" to persuade some metal to see things your way, the portapower is always an answer (maybe not the best).

They are as good as the person operating them.  You need to be able to think around corners when undoing collision damage and these are a useful tool

I don't see where that one can "Pull" rather than just "Push" so it is kind of limited.

The older I get the more I appreciate Porto-power. Have tool truck and HF versions. The HF one can do most jobs and accessories like a 5 ton mini ram fit right on it.

i should have bought one of these and kept my beater ///M

I have used multiple variations of these. The one you illustrate is kinda wimpy, and the offset foot is too brittle to do serious work. Also the similar one I used had seal failures early in service.