I've had Forsyth White Clouds for many years. It hasn't always been happy in my zone. It does not tolerate late freezes as it is a fairly early bloomer for me. The last few years we haven't had any late freezes and it has done very well. I don't have it planted under the best conditions (crowded in a small raised bed with several other daylilies) so it isn't performing up to its potential. However it does bloom sporadically over an extended period of time (June-late July) which none of my other daylilies do. Not sure if it is instant rebloom or what. I suspect that further south of me this cultivar would do exceptionally well.
I love the large flowers and if exposed to the sun the flowers turn very white. In shade or on cloudy days they can have a yellow or peach cast to them. The scapes are strong and are probably a bit taller in my garden.
Overall I would say if you live in an area that doesn't typically get late freezes in the Spring FWC will do well for you.