I have never registered a daylily and might never.. but I hope to one day register at least one. When I look at my seedlings just to pick which ones not to toss, I first look at the plant foliage. I have always had a thing about plant foliage, it doesn't all have to have the same color, or the same height, or the same openness, but it has to have the look that says I am healthy and vigorous. Scapes, now I hate a thin little weak leaning scape. I like a stout scape, one that will hold up three large wet blooms at once. I don't get many of those, but I keep hoping. I don't like short scapes, I prefer the 30-38 inch range. I like high bud counts when I don't think about deadheading, I like big plants when I don't think about spacing and spraying.
I love branching in my mind (often it doesn't look so great on actual plants) but still-I do check the numbers. I give away and donate a lot of plants so I much prefer ones that grow and multiply fast. If I did not do that I would much prefer plants that did not multiply fast and did not have to be dug and divided ever.
I know I would love pest and disease resistant plants, but I never really shop for them, I just seem to have accepted having to spray. I want everything to be very pod and pollen fertile.. Can't actually say many of my plants are sterile, just they seem to act that way for me. I love large bright eye catching blooms I can see and name from across the garden. I grow others, but they are just filler. I am a big fan of bloom consistency and uniformity and I would love blooms that did not fade till at least noon. I hate splotchy blooms, they are the worst, with some blooms just high humidity seems to enough to make them splotchy. I want blooms that open, not just halfway open. I want patterns that you are actually able to describe and expect the bloom to provide it regularly. I don't want a plant that rots, or that the foliage burns easily on it in full sun. I like plants that do well with very little care, but I love plants that show their appreciation and respond when given extra special care.
I suppose there is a never ending list of things, some we seldom even think of. Things like the clumps being easy to divide.. having a fragrance that a person like me could actually smell, sending up lots of scapes, just no end to all the wants we daylily people expect from our $20.00 plants.