They HF frames are both weak and may be out of alignment - top to bottom. If the alignment is good then you just need to a another layer of 2X4 bracing to the top and rear.
The as-sold wheel frame will move up and down visibly as you add tension - with the quick release handle you can wiggle the upper frame buy over an 1/8th. It is personal preferance if you want this action or not. It is a spring-like pressure and can be used to an advantage. I prefer greater rigidity in a frame.
If you are wheeling and getting ridges then your lower wheel has a radius and shouldn't have.
The HF machine also has a poor quick release and a cheap screw for the adjuster, if you work with a really good machine like an Imperial you'll see the differences immediatly.
It all depends on what you realistically want to make, if you are doing a door skin or the odd panel and weld with a skim coat then the HF machine is ok. If you want to make a highly metalfinished product then you'll need a better machine.