Time travel would be amazing, I get the weird feeling the most popular use for time travel would be for showing kids the dinosaurs and other prehistoric animals or to relive their favorite decade. Though it would be interesting to spend a week in Rome or other ancient civilizations and see for myself what was it like to live back then.Those times I wish Dr Who (or Star Trek in its time travel aspect "nuclear wessel") was real, would love to meet Marcus Aurelius and settle this. Seriously there would loads of questions I would ask him or many other historical figures.
Assuming language would not be a barrier, it would be neat to speak to scientists throughout the ages and maybe even preserve findings that were lost or intentionally destroyed.