Hi Clark,
Yup, the Apps Bloodworm works all year round.
Although I don't fish them that often during the more 'imitative' months (personal preference - prefer to fish buzzers or 'surface' flies) I would be extremely confident fishing one on the point with a buzzer on the dropper on any water in any conditions at any time of year. This is actually my cast of choice during the Winter months & also proved successful a few years ago when fishing a competition in sweltering heat.
I only tie them in Red and retreive in my typical dead slow to 'medium' figure of eight buzzer style retreive.
Also, as Hamish points out, watch out for takes on the drop!
Saying that they mimic a bloodworm kind of goes against the grain so when I tie mine with a segmented vinyl rib body I feel a little better.......I feel queezy when I see the ones with red beads for the body...eek!
Iain