[jQuery] id question

Hi
Is there a reason why: alert($('#id\{0}___').val());
not displaying the value, also no error with Firebug
but
alert(document.getElementById("id{0}___").value);
displays it ?
The html looks like this:
<input id="id{0}___" type="text" onblur="show_value()" value="123"
maxlength="10" size="10" name="id{0}___" />
show_value() run the alerts above
Thanks
gvg