yeah, the start was rather rough for me as well, but after a bit it become very similar to uq holder for the main plot. It is just very slow to start, even tho the shool/teacher/harem connection always remain present. I guess for me it didnt start to be really interesting until the big fight tournament (early version of the one actually going on UQ). Also the part regarding nagi, magia ereba (w/e is spelled), the vampire teacher and the primordial enemy, all things that are main plots on UQ, start to be very present after that arc.
But yeah definitely agree, its quite difficult to stick around negima considering the harem/ kid main char etc.