I really like post-apocalypse gaming. Not the "World War Z" zombie ones, really (survival horror isn't my thing), but rather the over-the-top Gamma World kind of game. Blasters, mutants, robots, half-buried statues of liberty.
I also really like fantasy gaming. Orcs, magic swords, spells, paladins fighting dragons, zombie hordes under the command of necromancers, etc. Piles of gold and jewels. The whole bit.
But I dislike mixing them in my own games.
For some reason, as soon as the "magic" is revealed to be "technology," I go a little sour on the whole thing.
I probably wouldn't mind playing in it, if I knew that kind of thing could happen or was definitely going to happen.
But it's not my cup of tea for my own games.
What's somewhat ironic about this is that I like both settings and I have a game system that would make adding post-apoc to my game trivial. As trivial as adding orcs into an AD&D game - just pull the stats out of a handy book. I know the rules will work, I know what the defaults for the PC's use of a "magic wand" that's actually .45 caliber would be, etc. The work is done for me. GURPS has plenty of books on the subject - Ultra Tech being just one of them.
I may at some point change my mind - I may run a one-shot or mini-campaign mixing the two. It would be a lot of fun to see how DF delvers deal with a post-apocalypse environment. I'm still undecided on introducing a form of explosives and black powder firearms into my game world. I'm leaning towards no, but it's an option I'm considering.
And I'm certainly up for busting out and re-starting my "Mutants & Mayhem" post-apocalypse game I ran a decade or so back for a group that included two of my current players.
But for my game, I just feel like the mix robs some of the magic from it for me, the GM.
So it's not likely to happen in my Felltower game. The magic is magical, not super-science. And I'm okay with that.