'Madge Cayse' is a very reliable double bloomer here; I have almost never had single or partially double blooms, and the few times that it happened, it was with only the first few blooms of the season.
The plant begins bloom here in late June; this year it bloomed from June 25th through July 18th (which is our ML season). This short period of bloom is due to the relatively low bud count, something that I agree with
@kousa about. While less than a month of bloom is not ideal, I have to balance that against the time of year of the bloom; at this point in the season we are well off of our peak bloom, many daylilies have not yet begun their rebloom, so the bloom and color of 'Madge Cayse' is welcome.
In addition to the relatively low bud count, at least for me, the scapes tend to be top-branched. I have never had it rebloom for me (but then, it is in a part of a raised bed where it gets a lot of shade, and it is lucky to get fertilized once per year). These issues, and the relative shortness of the scapes (24" for me is short; I prefer my daylilies taller, which is why this one is planted in a 22" high bed), are the big drawbacks of the plant for me. (I suppose another drawback is that sometimes the sepals show some green, and sometimes, for no apparent reason (thrips?), I have some buds drop.)
All of that said, the blooms are really lovely and generally open well here. I don't recall ever seeing rust on the plant (which of course is no guarantee of resistance and my memory could be faulty, but I have had it for decades now). These and its season of bloom are reasons enough for me to keep the plant despite its drawbacks, and even though I mostly "do" (or am trying to do) tetraploids these days. (At present it is one of only three double daylilies in my garden, out of (roughly) 150 registered cultivars, only 32 or so of which are diploids.)
If you want a really nice and reliably double daylily at a time of season when other daylilies may not be blooming (or are winding down), and the relatively short scapes and low bud count (and possible lack of rebloom) are not issues for you, then go for it.
