You pay for the quality that you want ... if you want to pay for vistherm then pay for vistherm.
Yes it is a plastic, abeit a hard plastic, but every plastic has its downfalls.
The won brothers one is leagues better. Not only do you have a seperate thermometer for the unit itself (displays the current temperature on the pro 2 model) this is more accurate then most other heaters. Why you may ask, because in almsot every other heater, the thermostat and temperature gage is all compresed into one cylinder. The won brothers temperature reader is to be placed, according to its instructions, at least 12" away from your heater. Now call me crazy, but that can be some pretty accurate readings.
Next, plastic can crack. Heck so can metal, but i ask you, what pressure does it take plasic and glass to crack compared to metal?
Again, with this hobby, you pay for the quality you want. It is up to you as a hobbiest to determine what you think is right for you
Lunchbox ... "i'm a man, but i can change, if i have to, i guess"
Tankless ... for now ... until i find what i really want (and what the wife lets me get!)