Just come on the thread. It's difficult to have a comprehensive view of all the developments as few of us see more than a few examples of electric bikes. Although I was interested in the Kalkhoff variants, I never got the opportunity to see them. The review of the cytronex interested me when my Giant Twist was off the road. I happened to be near Winchester and arranged a test ride which blew me away. I came back with a grin from ear to ear and bought one on the spot. Now, 6 months later, I am still very satisfied with my choice to the point of letting my Giant go, even though it introduced me to the pleasures of electric bikes. You can't fault a bike that still produces a smile of sheer pleasure when I silently beat up the miles to work and back.
Several members have commented on needing a larger battery. Actually, that doesn't seem to be necessary. In hilly Sheffield, the Giant managed the 16 miles round trip to work, occasionally lengthened to about 20 miles and an extra hill with a detour en route, usually pegging out on the last hill (fortunately short) in cold weather. The Cytronex manages exactly the same, often pegging out at the same point despite having a much smaller battery. Its the more efficient use of power in a lighter bike, plus the fact that having a bike that can be ridden much faster (and I do) means that I am probably putting more effort in myself.
So for me, the cytronex has to be the bike of the year, but I accept I have had no practical experience of most of the others.