Pros: Affordable, Well Built, Ease of Use and Cleaning
I have to say it never occurred to me that such a unit would exist until I was working at one of my companies events and they had a catered breakfast in which the caterers would cook omelets to order on these units. Even when I saw them I assumed like most professional oriented culinary gear these things would cost far more than they do. There really are no cons, for under $30 you can get a high BTU reliable, well constructed portable butane cook surface that is also designed with the ability to clean it easily.
I would say that dollar for dollar this is probably the best purchase I've ever made. I recently went on a camping trip and while hotdogs and hamburgers are always welcome, I was able to knock out some dishes like perfectly cooked sunny side up eggs, a chicken and pasta dish, etc. with absolute convenience. When it was time to leave it was simple enough to toss into a plastic bin I brought to hold my camping kitchen.
You could use this unit at it's lowest btu setting to warm a dish for entertaining, however you would want to have it in something heavy like a cast iron dutch oven, and most likely would want to stir it occasionally - it puts out a tremendous amount of heat.
That leads to one of the better reasons to have this on hand. If you are like many consumers, your kitchen is electric. There are a couple techniques that really don't work well with modern glass surface or electric burner stoves - stir fry with a wok, speed basting, are a couple that come to mind. Having this little unit on hand can fill the void and it will hide away well within a kitchen cabinet.
Lastly the fuel is affordable and lasts well. One canister of butane will likely operate this unit at high heat for over 2 hours (I have not timed this) and you can acquire the canisters in bulk for around $2.00 a piece.