I've lived in Japan for 2 years and had some experience with electronic translators. First, you pay for what you get so expect a good translator to cost a lot. Cheap out and get disappointed. Secondly, there are so many different functions on the good ones that it takes some learning on the functions so they can be optimally useful.
HOWEVER, they are really only effective if you have some foundation in the language you are trying to use it with. My wife is close to fluent and I am only conversational in the language. She is able to really make the translator worth her while. She can piece together long complicated thoughts with it when she is at a loss for words. I, on the other hand, don't know enough of the language on my own to really have it help beyond a direct word to word translation. I wouldn't recommend these devices for most people because they lack the language knowledge on their own and you can do a lot of stuff with limited language skills and charades anyway.