My LEGO Nexus Organization

So, quick question, since I never got to build anything in Beta(Due to being stuck in the Venture Explorer)...

How is building in LU different from LDD? Is it different? And if so, what are the differences?

Lots of differences. No brick outlines, no grid pattern to set up where you want your bricks to be placed, no incremental angles for hinged parts. (but those are just for building in brick mode)
The difference with model building is profound, You are able to group models and stack them together, where as LDD treats them as individual bricks that are together. (true, you can create groups, but this is tedious)
Behaviors are a blast, nothing like it in LDD.

Thats a short overview, let me know if you have any more questions!

When you say 'stack models', what are the limits to that? Like, could you stack something that's like a pyramid, or is there a limit to how it works?

Wow, I fail. Wrong word choice, I meant to say "Put next to each other" You can edit them in brick mode though, which enables custom building.

Ooh, I see now. =P

And are these models ones you obtain in-game, or ones you build and save a certain way?

You can collect models in-game, but you can also build models in brick mode, save them, and once they pass moderation they will work just like any other model.

For example, as part of winning Pod 7 I got a Pod 7 model that I immedialtely put on my Property.  As another example, as you go through Avant gardens, you will complete missions that give you the choice between House model packs and Castle model packs.  These packs contain several individual models that can be combined to build a castle or a house; i.e. "Castle Outside Corner Large" or "House Kitchen Model 2".  (Personally, I go for the castle model packs; they have more bricks, they sell for more money to vendors, and more people want them compared to the house models.  But that's just me.  :P)

Interesting, sounds pretty cool then.

What types of bricks are available, compared to LDD?

There's definitely not LESS of a selection. I'd guess there are more bricks in LU than in LDD, because of all the small "detail" bricks available in the game.

That sounds pretty cool then.

Are any of the newer bricks available? And what about colour choices?

I'm afraid I don't know much about the newer bricks in LU, but I can say this: the color choice is... pretty good. I've never found myself wanting more options than I had.

Are there any limegreen bricks? </obvious question from me> =P

I'm not sure if I should ask about minifig customization here, or simply start a new topic. The latter might be easier. =P

I know there's green, and I believe there's lime green :P ...

Well that's good. =) What about orange? Also, are there any bricks that have 'exclusive' colours, or are all bricks available in all colours?

All bricks in all colors--it's just like the LEGO Universe mode in the latest versions of LDD. ;-)

How does the selection compare to LDD Extended? Or is that what you meant by the recent LU Modes?

If you upgrade to the latest version of LDD, the LU mode has all the color selections LU has (or near all) LDD extended has more colors, and a few extra parts (such as electronics, and some technic parts.) It would be awesome if someone could come up with a list of parts available in LDD extended thats not in LU mode.

It would. I would; but a) I don't have LDD, and b) I likely couldn't run or install it. =P