re: Anyone been to Tanzania..

You do need to be a decent physical shape, and doing lots of slow stair-climbing wouldn't hurt. But the biggest thing will be how well you adapt to altitude, which is why I suggest taking an extra day. It'll cost extra and is well worth it.

Don't believe the summit rates claimed by the tour companies, they'll all say 95% or higher which is total BS. On the typical climbs it's more like 50% but goes up quite a bit if you grab that extra day (or even two).

ETA: The claim of 95% or more really refers more to how many people reach the crater rim. That's quite an accomplishment but is not the true summit and plenty of people drop out here instead of making the final push.