Also grants a glancing blow on your first attack while moving, which I consider to be the major advantage to the feat.
Having both maxxed out THF and TWF barbarians that have done everything in game i can say:
More targets or faster moving targets - THF is better
Killing mostly stationary targets, especially ones weak to stunning blow, or special weapon effects - TWF is better
Mobs with high DR you can't get thru, or are forced to use a lesser weapon to get thru - THF is better
Mobs that require very specific weapons its tough to get 2 matching ones of ... tends to be my THF guy for me since he only needs 1 and has some really great weapons.
So really both have there pro's and con. I like having 1 of each now, depends on the quest which one I take. Like - running with the devils elite - my twf guy with a couple wounding dwarf axes is better vs rainbow in the dark - my THF is much better due to all the elementals with the high DR you can't get thru.