Down 17% over the past 12 months -- and 83% over the past five years -- it hasn't been a lot of fun owning Transocean (NYSE: RIG) stock lately. But could it be that the suffering is coming to an end?One analyst thinks so. Nearly a year after initiating coverage of the offshore oil driller with a sell rating, megabanker Citigroup announced this morning that it's finally relenting, and upgrading Transocean to neutral.