[greiman]

I'm a little late joining the party, but I'll cast my vote too.

Assorted thoughts:
Partner's spade cards are well placed.
Partner's diamond cards are poorly placed.
If partner has a heart honor, that means my ruff isn't helpful.
In order to all of a sudden jump to game, declarer should have a 4 loser hand without 6 hearts.
My hand is awful, so partner should have some cards (or we've got no chance of setting this)
There's no point in trying to stop diamonds ruffs. Given our 3 small, they're unlikely to need more than one ruff anyway.

The worst hand I could give partner that let's us set this includes the CA and a major ace. And hope that declarer has x,AKQxx,AKxxx,xx.
I get my spade ruff, and then we cash our two clubs.
I could also give partner the aforementioned CA and another random KQ somewhere that declarer can't avoid. We take the first two tricks, and wait for our slow ones.
If partner doesn't have the CA, we'd have to take two spade tricks, a heart tricks, and something else in the wash.

I'm not familiar with the rating system here, but I'll go with something like this:
ST: 10
CQ: 7
Others: 1

And now you'll tell me that dummy had AK of spades and declarer pitched his losing clubs on the first two tricks.