TSLRF posted up a quick entry about getting into reloading - I was going to make a quick comment, and it turned into a long one, so figured I'd just post it up here.
I've been reloading for a few months now, on both single stage (Lee Hand Press) and progressive (Hornady LnL - I was going to get Dillon, but scored a great deal on the LnL). I'll be posting up some thoughts, pros and cons once I get some more loading time and experience under my belt. Stay tuned for that.
As Ryan mentions, in terms of pure apocalyptic 'survival' purposes, reloading has limitations and does not guarantee an unlimited supply of ammo. He mentions being limited to components on hand, which is indeed the big 'un.
Of course, that assumes that more components are impossible to come by - that may not be the case. People reload ammunition in the depths of the 3rd world, there are lots of half used containers of powders sitting on shelves around many parts of the country, components are more compact and easier to transport/smuggle than loaded ammo, and so on. Components might not be impossible to come by.
Black powder cartridges and cast bullets can help get around cartridge limitations, too.
Equipment breakage is another limitation, especially with progressives. Spare parts mitigate that, along with machining skill. My reloading mentor machined replacement parts for his Dillon 550 for the fun of it.
On the some of the 'survival' merits.
As Ryan mentions, the economics are appealing. The big 'un is shooting more today. Stockpiling more cheaply today, too. Stretch that ammo dollar as far as it can go. Even with ammo prices normalizing, you can save a lot of money reloading - half the price is pretty easy to do. So shoot twice as much, stack twice as deep.
Less often mentioned - you can reload premium stuff for much cheaper than buying off the shelf. When survival types stockpile ammo, it's usually FMJ stuff, 'cuz jacketed hollow points and other are just too expensive to do so in bulk. If you're a reloader, you can feasibly stockpile higher quality stuff.
For example: I'm working on loading up some Federal 147 grain HST jacketed hollow points. From the factory, these run $25-$30 for a box of 20 - over a buck a round, easy. My reloads will run me the grand total of about $0.20 each.
Similar story for rifle ammo.
Now, I'm not an advocate for carrying reloads in a defensive weapon today. There are a lot of reasons for using factory stuff for that. It is a good idea to practice with your carry ammo regularly. And, for a crap hit the fan stockpile, would you rather have Wal-Mart FMJs or premium JHPs to draw from?
Last for now - stockpiling components can give you more versatility versus loaded factory ammo. Does that pile of powder n' primers become 9s, 45s...223s or 308s, etc. What do you need? What do your buddies need? You have more ability to fill that need when starting from scratch...loaded ammo is what it is.