When I lived in Louisiana my local airport (SHV) had very uncompetitive fares, so I took Greyhound twice on long-distance trips...once to Idaho and once to Pennsylvania. In each case the bus dropped me off in the exact town I wanted to travel to, instead of the nearest town with commercial airline service. And in each case, it was much, much cheaper than flying (esp. SHV-Idaho...about $350 cheaper r/t which was a LOT of money to me then). It felt like it took forever but I met some cool people, saw the great wide open spaces of the western U-S, and generally had a blast.

Since then (my early 20's) I've ridden Greyhound once, and that was a 5 hour daytime trip. For day trips, I'd definitely consider it if the price and other factors make sense. For overnight trips, it's a miserable experience in a very, very special kind of way.

Regarding breaks: IME the rest stops DO occur near cheap-o eating places...and in some cases the actual station is basically a truck stop with a fast-food restaurant embedded. The drivers are usually pretty good about pointing out places to grab a bite and still make it back to the bus before it leaves.