They are great!
Ham antennas are usually brass wire in a fiberglass random and or not enough ground plane radials.
The J-Pole's copper 5/8 inch outer diameter has a wider bandwidth and a lower noise floor for receiving.
Plus it's an end fed 1/2 wave that doesn't have any loss, due to, not needing a 50 ohm matching system.
Only problem, it is exposed to the elements, like rain....Swr will go up slightly, And as long as it's below 2.0:1, your transceiver, will be good. Also, if you think of it, most commercial antennas are aluminum exposed folded dipoles.
The tarnish on the copper will not make a difference. I know someone who had made his own. It worked for 10 years until he took it down to give it to his friend.
For the best experience - Don't just click the "buy button" on the website. Contact KB9VBR by email and ask for the j-pole to be tuned for the exact frequency center you want.
Also make an air choke with your coax, five or six turns of coax at the base . This will prevent a radiating feedline and prevent distorting the antenna's radiation pattern. Or add sum uhf ferrites to the coax - makes a big difference in swr. I don't think antenna modeling programs take that into account.