I’ve seen articles for and against this practice.  In the Pilot episode of FRINGE, J. J. Abrams uses it... a lot.  And I’ve seen it several recent screenplays -- ZOMBIELAND -- I’ve read that this is falling out of favor and I've read that’s it’s still a sound practice...

Does any one have any insight... or better yet, the right answer?

Depends on what you mean...

THE WHOLE SENTENCE IN ALL CAPS?

or

The WHOLE sentence in all CAPS?

If it's the former, yeah, don't do it under any circumstance... It's sloppy and unprofessional.  If it's the later, and you're only using CAPS on words of action or sound... Go ahead. They actually want you to do this because it breaks the script down and makes it easier to find the breaks when someone goes back and rewrites your script for the 100th time.

Nice.  Thank you.

Save the CAPS for SOUND EFFECTS. Or some SERIOUS action.

Use SPARINGLY as OTHERWISE it looks like YOU'RE SHOUTING.

Oh, and it HURTS the EYES.

RENDEVOUS

It's a stylistic choice, imo.  I sometimes CAP whole sentences if something BIG is happening.  Some writers do it more often than others.  Some writers underline whole sentences.  It's a way to annunciate a piece of action or moment.

I disagree that it makes you look unprofessional since, well, professionals do it -- first timers and established.

I think the question is how do you feel when you read it?  if you don't like it, don't use it.

CAPS are used to draw people's attention to items of importance. This is usually essential character actions or props so that when someone scans the script over quickly, their eyes will hit the important elements of the scene (this is why dialogue headers (i.e. character names) are in caps). You'll note when you read a well-formatted professional script, you're eyes can scan the page and know the scene by hitting the stuff in caps (the slug, the characters, and the capped items that stand out).

Randomly placing the whole thing in caps? Well, if that whole action is that important, then it's fine. If you're going for eye pain, then don't do it.