For me it's probably like level 10. You'r all excited about your new build, you've just joined you guilds, and your low level skills are actually effective. Not to mention you don't have to deal with the late in game glitches, lag and whatnot. What level do you guys think is the most fun?

I was not aware that enjoyment was level based.

As I haven't gotten a character over lvl 50 yet I'd say between 15 & 35. I start relaxing and getting into my characters personality a little after lvl 10 and start getting anoyed about lvl 40/45, that their skills aren't improveing (I won't add skills to lvl).

I find the game most enjoyable between 15-35, seems challenging and at its most entertaining for me around there.

I really enjoy level 25-35 on expert difficulty the most. Still challenging, but not impossibly so. After I got to around level 40, it was less fun, even though I increased the difficulty to master. Probably because I maxed smithing and enchanting, and my weapons and armor were just too OP, despite not having used the alchemy-enchanting-smithing loop.