Mine behaves similarly. '02 3.0 gas. On heavy throttle it shifts pretty quickly higher up on the rpms as it should. On medium or decreasing throttle it tends to pause as you describe, like a big gulp, before shifting. Not ideal but I've learned to live with it. I'm also displeased with the downhill shifting and I normally put it in neutral on the steep streets in SF.

As for normal acceleration from stop, mine does a sort of 'quick shift' through the gears, or so it seems. The motor revs up quickly and then drops like its changed gears but it really hasn't. On harder acceleration from stop it doesn't do this so I'm thinking its a torque converter issue. I haven't been able to nail it down or do a deep enough search here to find any insights yet.