91 hours
level 51
Redguard, hack & slash
1.58 hours / level, though this is rising as level progression has slowed significantly.
Would be interesting to know as well, quests completed/hour. Gives you an idea of how much time is spent just poking around and exploring.
EDIT: 52 quests completed. Given the varying degree of effort involved with different quests, I've realized that it's not really a great measure.