My husband and I did Kili last Sept. We were on the Rongai route that
goes up one side (closest to Kenya) and down another. We chose
a six day trek and it was a perfect amount of time.
We used Adventures within Reach which is a CO based company who organizes the trek through EcoTours in Tanzania. They were ok...if you are not super rigid....thing will work out just fine if you use them.
Diamox was our savior. We are both super sensitive to altitude.
If you have the time, a Safari after the hike is fabulous!
We stayed at Bristol Cottages in Moshi pre & post hike. Super clean with a nice staff.
Hope that helps.