I like it in my current country because:
1) I'm not particularly fluent in the local language so communication with the cashier are more trouble than anything
2) there's one common line for all the self checkout, so you don't get stuck with picking the "bad" line
There might be two store employees if lots of customer, or only one if not many.
In other places i've been, they have a stupid limit of 4 registers per employee, with different lines for each grpup of 4, which brings back the "i picked the wrong line" problem. (Simple workaround would be to have one common area, and open as many registers as the number of employee allows.)