I have one of those Irwin vises that I use in my home shop. I think it's a 5 inch. I bought it off the clearance rack of Menards a couple years ago to replace the tiny little craftsman 3 inch that I had been using since I was a kid.
It works fine for what I use it for - small jobs, holding something while I cut it with a hacksaw, or run a tap through a hole or something like that.
It's not comparable to a professional vise - I have an old Parker 5 inch at my workshop, and apart from the width of the jaw, and the general shape, the two are nothing alike. The Irwin probably weighs 15-20 lbs, the Parker 50 or so. The Irwin opens about 6 inches, the Parker about 9. The Irwin handle is about 3/8 rod about a 10-12 inches long with what looks like a screw on cap on each end. The Parker handle is 1/2 inch diameter, about 18 inches long with big round balls on each end - you can put all your weight into it. You would never put a lot of weight into the Irwin.
The Irwin has a pretty nice swivel on it, with two locking screws, rather than a single locking screw. My Parker is stationary. It has a small flat behind the jaws that looks like you could hammer on it.
If I recall correctly I paid about $40 for the Irwin and $50 for the Parker, which needed cleaning up, but you don't find them that cheap very often. The Parker is probably at least 75 years old and will probably be around long after the Irwin is toast.
If I needed another vise I wouldn't hesitate to buy one, but if I had time to find an old heavy duty vise - Parker, Prentiss, Yost, Columbian, Wilton, etc - I'd go for one of them first.
but it, or any other vice, are fine if used within their limits. It applies to anything, Whilst that's likely not something you'd want to be using to free off frozen track rod adjusters or the like, it'll do fine for medium duty work. I've seen the best of vices broken when used outside of their limits or intended purpose.