Those at 4th kyu are good, also,etc.
The main difference is that, of course, there is more of a confidence of what has been learned in the basic level. (referring to 2nd kyu)
I'm more accustomed to grading that is related both to the amount of time one practices and to the improvement each person gains in relation to him/herself.
Therefore, I've seen so much variation among people with the same grade that I'd never generalize and say "those at 4th kyu are this and that". However, I would like to be able to say that "those at 4th kyu should be able to do this and that". But even that I unfortunately can't say, from what I've seen so far.