I can speak from experience: In fact, I suggest everyone read testimonials and email people who are actually using them. THEY are the ones who have experienced the benefits of the Hayhut first hand; not people who have seen them in a store and started making assumptions and excuses for not wanting one.
As to the "cheap plastic".. it is rotational molded poly. It is VERY strong. Here are other livestock products made from the same material. You can see one horse standing in a feed trough. (same mfg, but you have to buy hayhuts through dealers)
http://www.coonmfginc.com/ProductList.aspx
My mare who has a tendency to chew on EVERYTHING is too busy eating her dry hay inside the Hayhut and doesn't touch the hut with her teeth. If she has the urge to chew on something she chews on hay. This is the same mare who ripped her Shelter Logic hoop style run-in shelter to shreds within a day. So I do have experience with a VERY destructive horse and I had the same concerns only to find out my worry was all for not.
As to the plastic not holding up, there are STILL -12 years later - old versions up and working fine after 12 years that are made from the same material. (These are the old one piece style that couldn't be easily shipped).
I would never put an unprotected pallet in the field with horses. The pallet is to keep air circulation under the bale and prevent water from wicking up. With the Hayhut, because a horse can't get inside, you can safely put a pallet under the bale and keep it off the ground.
A rubber mat does nothing to stop rain water from ruining the bale in a downpour. It does nothing to prevent the horse from ripping hay out of the bale or using that hay as a bed or a toilet.
You'd be happy as well knowing you didn't waste 30% of the hay (based on the Univ of Minnesota study) to 100% (if a new bale got moldy) every time you bought a round bale.
Do the math, Hayhuts DO pay for themselves in a few months!