Ticafan,
Yes, they translate both ways. And, yes, to say the ticas appreciate it is a big understatement. These girls are basically young K*ds. To them it is a facinating toy, a novelty. You want my take on these things? No? Well of course you know I'm going to give it anyway.
First, I got a cheap basic unit (not the speaking one). I might have a different take on fancier ones, but I don't think so. These things can be very handy, especially, if you're stuck on a particular word, but they are no substitute for being able to speak some spanish yourself. They can be very useful as ANOTHER tool to HELP you LEARN spanish, but they have serious limitations as a tool to help you actually CONVERSE.
The timeconsuming process of typing in the word or phrase on the tiny keyboard is definitely not conducive to a naturally paced conversation and should be seen as a method of last resort. I suppose on some models you can type in the phrase ahead of time and store it, but how many phrases are you going to think up ahead of time and wouldn't it be better to just then learn to speak that phrase in spanish rather than push a few buttons and have some geeky device speak it for you? Also, they have a limited vocabulary, sometimes choosing an inexact translation, nuance or meaning of the word you were seeking. They don't always conjugate verbs well. If you, or more likely the chica, are poor spellers or typists, they don't always deal well with that well either. Finally, as long as I'm playing the devil's advocate or the voice of balance, say you get the $100 model, how can one argue against carrying large sums of money or fancy jewelry or watches around and then carry around a fancy electronic gizmo like this. It seems to me they would be natural targets for theives that see you messing around with one at a bar or on the street.
In short, a PDA translator can be an interesting SUPPLEMENT to your other spanish learning efforts or as a "BAIL-OUT" device when stuck on a word in conversation (or for those who waited until the last minute before their trip to start to learn ANY spanish), but should definitely NOT be seen as some sort of "MAGIC-BULLET" or substitute for learning to speak spanish by other means. Anyway, thats my take. Others may swear by them.