I've rather enjoyed a FO3 replay with no fast travel,

so only walking / running from place to place.

It's added immersion and at level 30 with just Point Lookout and the conclusion to Broken Steel left, it's been very nice.

Have you or could you do a 'no fast travel' play through?

I'm tempted to do the same for FO4.

I always do this, it's more realistic and adds a level of tension to the game wandering about not knowing what will come. Plus on mods that add food/ sleep/ drink requirements it means each trip has to be planned for.