I like using daylilies to obscure floppy daffodil foliage. I haven't allowed any to get too crowded into each other so I haven't had any problems with them. Rather than intermixing them much I plant clumps of daffs near clumps of daylilies. About the time the daff foliage is looking ugly is when the daylily leaves really start growing. Otherwise I mostly place clumps of bulbs between various perennials that may not cover as well as daylilies, but draw the eye away nicely. I don't use many annuals in the ground (aside from self sowing annuals), but when I do I typically keep them away from hyacinths or tulips because those bulbs prefer to be dry during summer dormancy. Daffodils tolerate moisture during dormancy better than most bulbs, but the leaves hang around for such a long time I've usually got all the annuals planted by that time.
