This depends heavily on the country that you are in at the time and whether or not they have good road maintenance of course, but for the most part I have found that just taking it easy and getting on a night train or even a bus, can be a much more enjoyable experience than flying even though it does take a lot more time.
Let's be honest: Unless you are very wealthy flying downright sucks anymore. It wasn't always this way, but I can't really remember the last time I had anything other than a borderline miserable experience when I fly somewhere. Between the really extensive security and the fact that for some reason, most people turn into absolute animals in an airport terminal, flying is quite possibly the most stressful method of transport these days.
If you are in most of the developing world, and believe it or not, even the United States, there are often night busses and trains that are much more comfortable than flying, and generally cost a lot less.
Although I have not traveled there very extensively, I was reading recently that night busses are gaining in popularity in Europe due to the high cost of the trains, and because people are completely fed up with the way airports are run. I can identify with this. I don't know what happened to turn airports into basically the worst place to be in the world, but that does seem to be the case.
This is a very popular way of getting around in China and South East Asia, and although it tends to be considerably less "luxurious" it is available in Central and South America as well.
one thing you need to be careful of though is to do your homework and make absolutely certain you are not being sold a seat on a minibus. Those night trips are just awful and you will be in a cramped seat with a driver that apparently gets paid more if he arrives 20 minutes early and is therefore cornering like a race-car driver.
Trains, even slow trains, are a wonderful way to travel but obviously this has very limited destinations.
Trains have the added benefit of the "white noise factor" that I really enjoy and generally are going to have a lot more space than a bus could possibly provide. I have slept quite well in these despite the rather flimsy mattresses and pillows of dubious origin. I would do yourself a favor and just buy a pillow for these journeys seeing as how pillows are available in every country in the world.
Even in expensive as hell USA I have been on a night train from NYC to Washington DC and it was one of the best trips I had been on in that country. You do need to keep in mind that in USA, almost all railways have to give priority to cargo and there are very few lines that are dedicated to passengers, NYC to DC is one of the few. It was $40 for the train and $200 for a flight between these two places and the security nonsense was almost non-existent for the train, the seat were huge, and I headed straight to the bar/restaurant car where I was quite surprised to find that things were reasonably priced!
One thing to keep in mind with this sort of travel though is that it is going to take dramatically longer than flying but on the flip side of this notion just think for a second how long flying actually takes: Between the hours before departing with all the security and perhaps immigration, your 2 hour flight is more like a 5-6 hour flight. With busses and trains the boarding process is far more relaxed but also, the arrivals cannot be accurately predicted (especially by bus) because there are so many variables at play.
For someone like me when backpacking, I don't really have a timetable that I have to stick to and even 5 years ago when I was doing this on the regular, the trains and busses had fairly reliable wifi on them but you really should plan ahead with a data plan if you want to get some work done along the way.
I am more of a take your time and don't stress yourself out sort of traveler, so for me night busses and trains are my go-to.
Another benefit of traveling by train if you are crossing from one country to the next is that the borders tend to have their own independent immigration stations, so you are only dealing with the amount of people that are on the train with you. There is no rush and no worry because they aren't going to leave without you!