I think that reading the documentation when you access a certain API function for the first time is a must do in any case. But having some good suggestions in the IDE the second, third, fourth, etc. time you access it and you only vaguely remember what the function expects/returns, is very useful. Instead of having to go to look into the codebase or the docs you simply look at the suggestions and most of the times you should be able to remember the info you need to go on.