Any serious student, writer or translator needs a good French dictionary. Lawyers also need to have one because French words and terms are regularly employed in law circles. Translation is big business around the world. With a translation qualification one is well placed to make a decent income if they know their niche well. It also possible to perform simple translation using French translation software. Carrying out French language translation using software does not make the use of a French dictionary obsolete; it remains software which just like a machine does fail.
Dictionaries are not cheap but you do not have to buy each copy that you need. You can easily confirm the meaning of a word by going online and checking it. English to French online dictionary are as accurate as the paper copies, what is more sometimes they come with forums which provide discussions on words submitted by patrons and these too can help you find the right meaning for the word you are looking for. Free translation from English to French is also provided by some sites like yahoo and Babel fish. They are not known to be very reliable and you will still have to check your work very closely to avoid embarrassing errors. Some dictionaries are geared towards translation like the French English translation dictionary.
Deciding on which dictionary to buy depends on your particular needs and level of language fluency. You can buy English to French dictionaries if your English is your strength and French to English dictionary of French is your strength.