This appears to be about the best possible way to share large files with friends and family. You don't need to set up an FTP site, or get a .Mac account with a public folder, or mess around with emailing a giant file (and risk that it won't be received).
Pando works kind of like a Bittorrent client. You add your files, it generates a .pando link file, and emails that off to whomever you want to pick up your file.
That person then opens the link, and via the magic of P2P file sharing, gets the file from you and from anyone else who has already received the file and has Pando running.
But here's where it gets good: It ALSO sends the file to Pando's "super-node" servers, which means that there's always at least one "seeder" online at any given time. So even if you quit Pando and go away, your recipient can still pick up the file. (Within 14 days of its upload, at least.)
Basically, it's like BitTorrent or Gnutella with a super-fast peer in the mix. Or, alternately, it's like Pando sets up an FTP server for you, plus it works even faster if there's more people online (since they'll all feed the file, thus increasing the speed of downloads).
But just because it's P2P, it doesn't mean that this is for illegal files or wahtever. This works just as well (better even) for sharing photos of your kids with Grandma, or swapping a few big Word files with classmates or colleagues.
It's not secure (well, it's a little secure, but don't send your taxes this way), and there's still a few bugs (it's beta), but the app works great already and is only getting better.