I don’t have a PUK 2, but I have had a PUK 3 Pro for a year and a
half. I can tell you about that one. I work mostly in gold and
platinum, with occasional silver repairs. It’s great for tacking
heads, prongs, or other parts in place that might move during
soldering. It’s wonderful for welding jump rings on charm bracelets -
no worrying about keeping a loaded bracelet out of the way of the
torch. It’s great for repairing broken ear posts on earrings with
heat sensitive stones without removing them. I’ve found the welds to
be more brittle than soldering, so I drill or bur a depression for
the ear post, weld, then build up around the base a bit to reinforce.
Tongues on clasps can be welded without annealing the metal, so that
it holds its temper. Pits in castings can easily be filled in.
I haven’t found the PUK to be good for sizing rings or welding heavy
pieces together securely. It’s hard to get a lot of depth, and it
takes much longer than just soldering. Working on prongs or bezels
right next to stones other than diamond or corundum requires masking
them to prevent tiny flying beads of metal from chipping them.
It takes a while to get good on it because you have to experiment to
find what works for each situation. That said, I find that I use it
almost every day.