I haven't seen discussion on GAF recently for planet sizes. They're talking about the 128 meter digging limit right now: http://www.neogaf.com/forum/showthread.php?t=1243852&page=27

This is the reddit discussion about planet size: https://www.reddit.com/r/NoMansSkyTheGame/comments/4svkci/a_concise_visualization_of_planet_size/

Does it simulate gravity correctly? It would be hard to stay grounded or get any traction on tiny planets.

Gravity is identical on every planet and spaceship.

I've always thought that too, but if you watch the video showing the jetpack the description suggests the gravity varies. It might not be but it does open up the possibility:

it's looking pretty good.

It was said a while back that the suit compensates but what if it can only compensate so much until you upgrade it?

Missed opportunity. Vegetation could vary from mile high trees in low gravity to short stubs and mostly flat wildlife in high g. Maybe that's still in there to some extent. Changing the gravity immediately gives it an alien feel. Seems there is plenty variety already, moving around in 0.1g to 9g might be too impractical. (Elite Dangerous cheats too so you can always take off with the max 2g thrusters and keep good traction on low g planets)
Still wouldn't mind seeing the (imagined) effects thet gravity, temperature and different atmospheric presure / contents can have on life.

Gravity might affect the planets. It's only confirmed it doesn't affect the player.

ED seems to have it implemented well, although the driving itself always feels bad to me.

That's probably just lore, but could mean the jet pack is disabled on certain planets. That would make non of Sean's past comments wrong.

New video was leaked early. It's badly edited and not great quality, but someone took a screenshot. Look at the bottom right:

Might as well post it for now:

http://webcache.googleusercontent.com/search?q=cache:https://www.youtube.com/watch?v=LrBjP8M-sco