i noticed that tiger updated my airport express base station when i went into the 'airport admin utility' - configure. the update didn't show up on software update (unless it appeared within the 20 minutes since i had last happened to check) and at no point was i told that it was available so, in effect the update was just lurking, hidden and unused. appears that i'm getting an improved signal now. my apologies if this has already been noted or if this was a case exclusive to me.