Matchpoints vs. IMPs -- do you know the difference?

A bridge friend, Bill Kreps, has always said that even good players don't play IMPs well. They play matchpoints so often that certain habits are ingrained. He claims that we all know the difference between IMPs and matchpoints, but don't shift gears correctly. This deal is an example of that:

In third seat, East opened 2♦. South, an expert who is playing on one of the U.S. teams in the Bermuda Bowl (the world championships) in Bali, Indonesia, later this month, was South. He overcalled 4♥ which was passed out. I believe I would double, then bid 4♥ as you can play in three suits. It doesn't take much to make slam, say the club ace, spade king and not much else. But as Shakespeare said, the play's the thing.

West led the ♦Q, declarer played low from dummy and ruffed. Do you notice anything?

Yes, as long as trumps aren't 5-0, you can draw trumps, knock out the ♣A and claim 10 tricks. That's not what South did, however, or there would be no story.

South next led the ♠A and another with West winning the ♠J to lead the ♦J. Declarer ruffed, ruffed a spade in dummy, led a club from the North hand, and the contract was in jeopardy.

East ruffed, played the ♦A, and South was in a pickle. He ruffed with the queen and played the ♥A and ♥K. West had started with ♥8 6 4 and his 8 was now high for the setting trick.

Here are all four hands:

Notice that even in the end game, declarer could have made his contract. After ruffing high, he could lead a low trump to dummy's jack, then lead a club. East is out of trumps, so that works. Declarer couldn't picture that East had five spades, however. He wouldn't have been in that position though, if he had played the deal in a straightforward manner. Get the kiddies off the street. No use losing two trumps tricks with J-10 vs A-K-Q-7-5-3 now is there?