Here's what happens: I hit the gas, and it revs like a beast, but hardly accelerates at all. It's getting so bad at highway speeds that I avoid going over 55 MPH and opt for back roads (where it still happens, but less likelihood of getting smooshed by an 18-wheeler.)
I bought the car 2 years ago(it's at 158k miles now) and it's behaved impeccably until this issue started a couple months ago. A friend of mine said it could be the clutch starting to go (I don't know how old the clutch is -- it could be original equipment.) There's none of the behavior I would expect of a bad clutch -- difficulty going into/out of gear, noise when shifting, need to double-shift to get into first gear -- but nothing else springs to mind.
Any suggestions appreciated!