I'd go with something like this, although if your race was at Monza or Spa, Force India would be well up at the front.
I think Brawn and McLaren are probably the best packages at the moment, with Red Bull, Ferrari and Williams just behind.
I haven't got a ruddy clue where Toyota are, they can be both frontrunners and backmarkers at the same race (eg. Singapore). Renault are being served well by Alonso, who's outperforming the car imo (but can we wait 'till half way through 2010 to see if Alonso is as good a driver as I think he is - not nearly as good as EL_NANDO thinks he is however!)
I think BMW have stepped forward. I think Toro Rosso are clear backmarkers. But at the end of the day, its so unpredictable, the only constants have been Ferrari, they've been in that 3rd-10th position all season in quali, sometimes (Spa) gaining advantage from KERS to get higher.