Whether using an XP glitch in Skyrim is cheating or not is really down to the individual. While it is certainly not what the game developers intended, it is still possible within the base game without the use of mods or console commands. In my opinion, this certainly means that you could argue against the cheating allegations.  However, if I wanted to get the full Skyrim experience as the developers intended, I would shy away from this exploit as it seems rather unsporting.