Just a few of linguistic observations after 15 years in Taiwan.
1. There really isn't a superb dictionary for translation in any language. Translation is an acquired skill that accumulates along with one's knowledge of the language. Just as nuts and bolts alone won't make an automobile; words along won't make a language.
2. Locality has a lot to do with usage, idiom, and pronunication. Traveling a hundred miles in the U.S. will demonstrate that people choose different words, expressions, grammar, and pronunciation regardless of what we imagine. In the case of Taiwan versus Hong Kong versus Beijing it is even more contrastive. I have a word count reference that compares Mainland China's highest frequency usage to Taiwan's. Mainland China uses more of a modernized, military vocabulary; whereas Taiwan retains much of the older agrigarian imagery. Even the differences between north and south Taiwan are quite different. Southern Taiwanese are far more willing to code switch between Taiwanese, Japanese, and Chinese; while in Northern Taiwan people tend to express wholly in one of the three lanaguages at one time.
3. More dictionaries are useful because one is never perfect. Dictionaries alone won't make one a master of a language. After all, most of us learn our first language by avoiding dictionaries and just asking others to clarify meaning.
In my own case, I use the PDA for speed and convience. If I am reading on the computer, I still turn to the PDA for searching reference to characters on the screen. It seems the platform is as much of value as the lexicon. And the fact that the PDA will do fast searches just offers me a lot more than any bound reference text. But, in 15 years of teaching English as a 2nd language in Taiwan, I must say that any and all dictionaries when used alone will provide a very distorted view of English. Why should Chinese learning be any different? It is about the imperfections of learning a 2nd language from merely a book. I suspect one can learn more Chinese in a pub than any library. After all we are social animals.
Finally, the greatest problem I've run into is 'double translated' dictionaries. Many of the English-Chinese-English dictionaries that I first acquired in Taiwan originated form English-Japanese-English dictionaries. So the interpretations had a Japanese cultural spin in the first place that was carried over in explaining English to the Chinese and Chinese to the English. In other word, if you want to learn good English, have an English autority provide the text; if you want to learn good Chinese have a Chinese scholar originate the text. And if you really want a good dictionary, it is likely to be in one and only one language. Most of us can only use one language really well - like most of us are either right or left handed.