It's the ability to beat the top teams, but fail at the strugglers, which shows an inconsistent outfit, which usually leads to a mid table finish.
I don't think Southend are that sort of side at all though. They may or may not be up there later in the season, but it's not like our results and performances against Leeds and Southampton over the last couple of years, or that Wigan game you alluded to.
Southend are to my mind an extremely sterotypical League 2 outfit in their qualities and the way they play. For me the thing to take away is that we beat them comfortably, and that as at this moment there's no one playing better - results wise - than them, that we have shown we can beat exactly the sort of side League 2 will throw at us, regardless of position in the table.
Oh yeah, and we beat Crewe (19th) and Barnet (21st) and lost to Shrewsbury (5th) and Oxford (6th) anyway. So there.