I may be the oddball, have taken mk677 for 8 months with 5 months off, and back on it again, however, I only recommend taking it for 6 months straight for best gains, then take some time off.
I get very good energy from day 1 with it at 25mg every morning, very nootropic, positive mood, super vivid wacky elaborate dreams, absolutely love the stuff, better thinking and cognition as well.
In the gym, increased recuperation from workouts, 20 to 30% increase in strength over time, nice pumps.
However, one of my friends who takes it can only tolerate 10mg or so as it makes him tired and lethargic, everyone reacts differently.
I am 49 years old, and it brought me from baseline level of high range for a 49 year old to the high range of a 16 year old hgh and igf-1 wise, so could not be happier.
Sleep is great from day one with it, but after about 2 weeks on it, sleep is quite good, but never had problems with sleep before the stuff anyways.