Speaking for myself and knowing that I am at the higher end of the curve at one month after activation there is a definite improvement. With the processor on my auidogram is almost normal, a 10 to 20 dB loss. My word recognition score went from 44 to 64% and more improvement is expected. Household noises have returned, sometimes I understand my wife from another room, we went to a restaurant last night and I could understand her easier then she could understand me.
After a couple of weeks when the site has healed yes, the external processor comes off at night.
The processor can be large, I would say that mine is the size of a large BTE, but they are getting smaller. And both Cochlear and Med-El have an off the ear option, basically a disk that just attaches over the implant. I chose the behind the ear one at this point because I think it has some tech advantages but Cochlear is in the process of updating their off the ear version, probably be released next year.
I have been documenting my experience in a thread here.