The main advantages with the Delta One is the size. They are very compact and come with really nice accessories. They have very distinct clicks for diopter adjustment which I enjoy.
Optically speaking, they are good, but I do not get the same "WOW" factor with them as with the rest of the series like the Forest II and Chase ED. I find that binos such as the Vortex Diamondback 8x32 and the Meade Rainforest 8x32 are basically in the same optical zone as the One. Speaking about the whole package though, i find the One 8x32 a bit tough to beat.