I don't really have much to add on my side, I haven't played many Dreamcast games, but what do you guys think is the best/coolest use of the VMU screen on the controller in a game?

I always thought the additional info that was displayed was good and hoped that it would carry on.  A small LCD screen should not cost much, hell that thing was 20 bucks back then so today, it should not be so hard to implement it.  My faves or ideas
NFL 2k, play selection so that if playing with someone in the same room, they couldnt see your play calling.
RE Code Veronica, the VMU would always display your health, so it was useful to just look down instead of going into the menu screen.  Especially if you got poisoned or something.
NBA 2k, think you could do something where you sub in players using it.
Another example, maybe cumbersome, but would add that sense of having to look elsewhere would be ammo counts.  Yeah, games have it on screen and some do it on the weapon itself, but it would be pretty neat, and add more to a sense of immersion where you have to look elsewhere, like the gun to get the ammo count.
Yup, just a bunch of uses where extra info can be displayed where you would normally look at the pause menu and instead see it on the little screen, to keep things immersive.  RE games and RPGs might benefit the most.

Cupil playing around on the VMU screen in Skies of Arcadia.

i remember on virtua tenis u could actual see the gameplay in real time

" i remember on virtua tenis u could actual see the gameplay in real time "