As someone who likes long drives
but can't drive for more than a couple hours straight, I've grown accustomed to sleeping or just stopping at rest stops. The variety in the quality of the rest stops (especially in the Northeast) is impressive.
States with good rest stops:
Maryland: In addition to the nice mall-ish rest stops on Interstate 95, there are also some very accommodating and comfortable places on I-70, for those of you traveling to or away from the East Coast.
New York: Not much in the way of fancy food places or welcome centers, but the rest stops are generally clean, spaced fairly close together, and always open 24 hours (see New Jersey).
Maine: Well, it's not like Maine has a lot of highways to stick rest stops on, but the tolls from the Maine Turnpike have resulted in a number of nice rest stops on Interstate 95.
Poor rest stops:
New Jersey: Yuk. In addition to being nearly impossible to find, Jersey's rest stops are not very clean and close early (~10pm), not good news for those who drive at night.
Massachusetts: Many of the rest stops on the Mass Pike (Interstate 90) are now under construction, making them less available than before. Spaced close together, which is good, but generally not nearly as nice as other states' toll road rest stops. If you are travelling on a highway elsewhere in Massachusetts, don't even think of looking for a rest stop; the only ones that exist are poorly maintained and never have bathrooms, and are occasionally closed to deter drug dealers.
Well, I've mostly driven up and down the East Coast, so most of my rest stop experience is in these states. But in my couple times across the country, the rest stops have seemed uniformly very good in the Midwest and uniformly mediocre on the West Coast. I do remember sleeping at good rest stops in Missouri, Michigan, Kentucky, and South Dakota, while I vaguely remember poor rest stop experiences in Wyoming, Vermont, Ohio, and Oregon.
: After a recent (6/2001) trip through Mass., I noticed they've upgraded a bunch of their rest stops on 495
. Brightly lit and spotless rest rooms (see how long that lasts...), but they close at 8pm. Still a big improvement.