My friend Stuart made the very nice point that time travelers being chased by a T. rex that looks like Big Bird is kinda lacking in... well, in something. So the popular representation of dinosaurs as feathery probably won't stick, no matter how scientifically accurate it may become.
After I laughed, I thought about that seriously, though... like I said, the big dinosaurs probably were rarely (if ever) feathered as adults. Also, if they did have feathers, it'd more likely be downy fluff, not contour feathers like birds today have. And I disagree that it's necessarily a problem. One of the few scenes from the movie 10,000 B.C. that really worked well was when they were all fleeing and hiding from the terror birds. And anyway, a down-covered T. rex would look kinda wooly and freaky cool, in my opinion.
That said, yeah. Dromeosaurs were almost certainly all feathered (examples of many, many species with feathers have turned up over the last few years) and that annoying kid at the beginning of Jurassic Park himself said it: being chased by a giant turkey isn't very scary.