I've shot a few rolls of the J&C Pro 100, though I've only gotten two developed so far. My first roll had the sky areas in three frames marred with bubbles under the emulsion (look like a negative image of a galaxy, almost). I found no emulsion defects at all in the second roll, when I dispensed with the acid stop bath (I had already been developing at 68 F), but that roll was pretty badly scratched (rust in the film path in a camera vintage ca. 1927 -- since carefully removed using methods successful in previous occurrences in other cameras). Some have reported the problems with pinholes and bubbles to be intermittent, so I can't consider my results conclusive yet -- but I have another exposed roll, and 3 more in cameras, plus four more waiting to be used; by the time I've exposed, developed, and viewed all of that film I should know enough to decide whether to make another purchase.
In terms of dev times and reciprocity characteristics, J&C says you can treat it as APX 100, but the soft emulsion makes it obvious it isn't just APX somehow obtained in bulk at a huge discount and recut -- in fact, it's apparently coated specifically for J&C on antique machinery somewhere in China. The backing paper is crude, but effective, and with practice I've gotten better at seeing the (faint white on the black paper) numbers and markings through the ruby window. The film now includes a 120 size film can with each roll, which should cut down mightily on edge fogging after exposure (but still, load and unload in the dimmest conditions possible, the backing isn't as tight in the spool as Kodak). The spools themselves are quite nice, very similar to the one that came (from the Ukraine) in my Moskva-5 when I purchased it -- well molded plastic with a chamfer around the key recesses to ease insertion, and they fit perfectly for both length and key size/profile in a variety of cameras. The film also respools more easily than Kodak for a 620 camera that won't accept a trimmed 120 supply spool.
Imagewise, it's excellent -- after processing for 22 minutes in HC-110 G, agitation every 3 minutes only, grain is almost invisible at 2400 ppi scan (sorry, I don't have my enlarger and bathroom darkroom set up yet), sharpness is excellent, and the film appears to have very good latitude (I get very good recording of textures at Zone II, better than what I'd expect with TMY at the same level of underexposure). J&C claim it takes expansion and contraction well, and stains well, but I haven't tried any of that yet. Maybe I'll do my next roll in Caffenol; the tanning effect might also protect the gelatin a little.
I'd be interested to hear if anyone has success using a hardening pre-bath to reduce the emulsion problems, but I now think the main key will be to avoid the sudden alkaline/acid transition of a stop bath by using a water rinse instead, or going directly to an alkaline or neutral fixer (used one-shot to prevent developer carry over from causing problems).
