I think the way IN and OUT mark in the timeline are working in Kdenlive is quite strange. By the way it's different to any other NLE and I don't think it's a better or more intuitive way.

I think IN and OUT should be use to select a part of the editing to do 3 point editing (like I said in my other post : http://www.kdenlive.org/forum/3-point-editing) or to do CUT or LIFT.

Here a example of CUT or LIFT (Letter are frame, # is a hole in the editing) :

TIMELINE | V1 | ABCDEF i GHIJK o LMNOPQRSTUVWXYZ

CUT : TIMELINE | V1 | ABCDEFLMNOPQRSTUVWXYZ
LIFT : TIMELINE | V1 | ABCDEF#####LMNOPQRSTUVWXYZ