Is it always a bad practice to catch System.Exception?

Please consider the following piece of code, which throws three different exceptions (namely, System.Configuration.ConfigurationErrorsException, System.FormatException and System.OverflowException):

int SomeInt = Convert.ToInt32(ConfigurationManager.AppSettings["SomeIntValue"]);

The exceptions are different, and so in practice I should have three different catch blocks to handle each particular exception. However, in this particular case, all exceptions are handled the same way: a log is written to, say, EventViewer, and a message informing of a configuration error is displayed... In this particular cause, is it too bad to use

try
{
    int SomeInt = ConfigurationManager.AppSettings["SomeIntValue"];
}
catch (Exception ThisException)
{
    /* Log and display error message. */
}

or should I, instead, use the three catch blocks and repeat the code within each of them?