I'm having pre-trip worry--I've read several accounts of hostals not having your reservation when you arrive, even if you already put a deposit down. Is it a good idea, then, to reconfirm before you arrive to make sure your reservation is still being held and not "lost"?

YES! I always recommend REconfirming the room about 1 week before arriving either by email or a telephone. It does happen sometimes that reservations are lost. Also, if you arrive later than you originally said (and don't call) they almost always release the room to the first person to arrive. Keep in mind that most hostels keep their reservations in a reservation booklet written in pencil -- you rarely find reservations being kept on computer.

Good luck and DO REconfirm those hostel reservations!

Saludos, MadridMan