In PgAdmin III, when I copy value from returned grid and paste it into the query text, it appears there in double quotes. But to use it in query, in where clause for example, it has to be marked with apostrophe. So I have to replace quotes with apostrophe. It is rather weird for me that I always have to do so. Why it is designed in such strange way? This is a kind of stupid theoretical question, I do not expect any practical answers :)
You can customize the quoting character, by following the following steps.
It should work, you may need to close and open PgAdmin-III
EDIT: For Mac OS X the option could be found in pgAdmin3 > Preferences > Query tool > Results grid