I don't know what it is for me, but while I love delta 100 in sheets, and rollfilm, I'm not a fan of delta 400 in any form. I much prefer hp5 as a faster film. I don't find delta 400 to simply be a faster version of delta 100, although I originally assumed this. It's different. Somehow. Duller. Negatives are thinner. It could be me. Please tell me I'm wrong, and I will try it again. I didn't like it. Believe me, I want to love it.
Now, if a vote could be cast for an expanded line extension of their films, I would much prefer panf 50 in sheet film. I'd also like to see it on their ULF offerings. I'd buy a heck of a lot more slower film for my older cameras. Some of the stuff that they offer in that program for older cameras only appears as HP5, and really makes little sense at that speed, but I buy it because unless I can slit it myself from something else, there's no other alternative.