They are for temporary use, as the sidewall printing states. If you have a large truck, SUV, or off-road vehicle you probably already have a conventional spare, as you should. For most of us the temporary spares are just fine. I used the one in my 89 Accord a handful of times in the 23 years I owned the car and it worked just fine, even for a 100 mile trip home from Possum Kingdom Lake. You can definitely feel the difference if you have to use it on the front. Like anything else on your car, maintenance is key. Set some kind of reminder to check the air pressure at least twice a year and when you do visually examine the tire for signs of deterioration. I never noticed any on the Accord's spare. It's not exposed to UV or road conditions so it ought to last a very, very long time.
If you have to use it, use it with common sense. Don't drive 100 mph in the middle of the summer and don't flog it on dirt roads for very long. If you sleep better at night having a conventional spare then, by all means, get one.