I would say don't ever use the "Take Offline" thing in the GUI unless you know for a fact that the database is not in use. By anything. That's hard to know without doing some legwork, so why not save this script somewhere and always use this?
ALTER DATABASE $dbname$ SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
ALTER DATABASE $dbname$ SET OFFLINE;
And then the reciprocal of course:
ALTER DATABASE $dbname$ SET ONLINE;
ALTER DATABASE $dbname$ SET MULTI_USER;
The reason you need to set it to
SINGLE_USER first is to kick out any existing users (there is an option to do so on the detach dialog, but not the take offline dialog), since SQL Server needs exclusive access to the database in order to take it offline. Now, you may want to do some extra legwork anyway to see who is currently using the database, as if you do this in the middle of a large backup operation or ETL job or what have you, that might be problematic.
EDIT : I have filed a suggestion on Connect about this (see Connect #2687832) and have also posted it to Trello (filed under "Object Explorer").