I prefer walking, its so interesting finding new places each time and having new random encounters. Fast travelling seems rather to me.. I'm a sucker for immersion, especially with random encounter and more npc mods installed.

It depends, I like to role-play so I tend to walk then but if it's a loooooooong ways away I'll fast travel.

I try to walk to the area to keep it real and challenging. I fast travel when I'm in a hurry but I walk more than I fast travel.

i mainly fast travel when the location is to tedious to walk to otherwise i prefer to walk

I like walking but sometimes getting "THE CEASAR HAS MARKED YOU FOR DEATH, PREPARE FOR BATTLE" ever 2 minutes can get annoying :c so I tend to Fast Travel.

In my first playthroughs i walked a lot around the world, but with every new game, you fast travel more ^^

Like many others here, it's largely situational. However; I'll only use fast travel if I'm particularly impatient that day. To anyone who's familiar with the mod A Devil's Wish, you can get a teleport ability similar to "blink" from Dishonored. Usually I'm sprinting and warping. If not that, I'm using the motorcycle mod, or if I feel like giving a massive middle finger to lore and logic, I'll use the jet pack mod. I'll only fast travel if I somehow don't want to use any of that.

Yeah Im just like JSev33 Motocycle or Jetpack, the jetpack reminds me of GTA San Andreas, fun fun fun or there is a mod that allow you to ride on creatures backs like deathclaw which is bad ass, but when Im not doing any of those I just walk and kill every thing on my way that is hostile, I rearly use fast travel, and I have compleated fallout 3 ( 3 times on consoles and 4 times on PC ) and still walking around looking for an adventure  

I've been using XRE cars lately so fast traveling is out of the question, unless you're fine with leaving a car worth six thousand caps in the middle of nowhere.

I like walking myself because you can always get those random encounters and I just like seeing that. Makes the game more interesting, at least for myself anyways.

Occasionally I play around with mods that disable fast travel or provide alternatives to it, but on most playthroughs I'm too impatient to walk the whole thing and I just fast travel.

In Fallout you don't have a horse or car(unless you have that XRE cars mod) so I usually fast travel a lot in Fallout. But in Skyrim you have a horse so it makes not fast traveling more enjoyable. Over all though I would go with fast traveling.

I'll admit I am a fast traveler. I walk first when you have not discovered a place yet, but once I get enough markets discovered I fast travel everywhere. I just get to impatient to walk all the way back to my home base.
I don't use the other mods mentioned in above posts but if I did have a motor cycle or car then I'd probably not fast travel as much as I do.

At first I walk than fast travel if location is on other side of the map, but lately I have been using XRE Vertibird.

I prefer walking and running around wastes.

I always walk. Fast travel is not an option for me, it is jist so role breaking. The wasteland is harsh through and through, and traveling can be dangerous, expensive, and fun!

Most of the time just walking around the wasteland...
Or using my stealthy light armored build, running sneak around the wasteland, lol...

I try my best not to fast travel as I like walking, but sometimes I get fed up with walking to the same place a hundred times.

I really enjoy walking the Mojave due to all the mods i have installed. With enbs weather effect mods and random encounters walking in the mojave can change from a boring task to a new beautifully dangerous mystery. Especially when you add new towns and play in hardcore mode. The game is just so much fun!

I love walking and exploring. It actually feels like your venturing off on a mission or quest and you take in and experience much more of the world, you end up loving it so much more, as corny as that sounds haha.
Think Morrowind and how much everyone loved that game and all it's sights and sounds. It was quite the epic adventure...
However, yes I do fast travel from time-to-time, as it can get pretty repetitive and boring.