Here's two things I've been thinking about:

How do Norm and the other avatar drivers get their driver hours on earth without an avatar? (Grace:"have much linktime have you logged" Norm: "about 520 hours")

The other thing I dont understand fully is how the matechoosing among the Navi work? When Jake and Neytiri has the "and you may choose a woman" talk it sounds like the men decides who they want and the women has no saying in it (even though Jake wants Neytiri to choose him as well, but he's a human after all).

But on the other hand it seems like Tsu'Tey already has choosen Neytiri (Grace tells Jake that they'll become a mated pair and so on) and if so, she shouldn't be able to go with jake instead.

But it seems to me that the Na'vi are too peaceloving and in balance with nature to be the kind of people that forces their people (women in this case) into things. It also seems like the women and men are quite equal and have no gender rolls.

But then again, if the women can choose as well as the men, what does the whole "choose a woman" thing mean? Any thoughts?

I guess there must be some sort of virtual reality programme. I wondered as well, more because their avatars "fully mature on the flight out" as Norm said.

I think here it is specific to Jake. Neytiri is saying to him "You may choose a woman" because she wouldn't exactly say "You may choose a man". I think you are correct with the gender roles being a bit ambiguous, but ambiguous in a good way. Women and men seem to have equal roles in Na'vi society; there are female hunters and even the leaders are equal, olo'eyktan and tsahik.
I do, however, believe that there is a special distinction for the Na'vi who will eventually become olo'eyktan and tsahik. There is some sort of system that keeps the leadership in the family as it were. The child of the olo'eyktan and tsahik will always be the next olo'eyktan or tsahik, who then is mated with the best prospective member of the other sex.
Those are my thoughts anyway

I'd guess it was a virtual reality thing too. The entire "Choose a woman" seems inconsequencial to me. Jake is told he can "Choose" But I think this means that now he is a member of the Omaticaya clan now, he CAN have a female. It doesn't mean the woman HAS to go with him. Neytiri and Jake are in love, plus he does say "This woman must also choose me" and so inclines that the two must want each other. Tsu'tey and Neytiri haven't mated yet because Neytiri doesn't really love him. I mean, did you see the withering glare she gave him after this line "Jake Sully will go first"
Neytiri just glares at him. So, personally, I think it just means that he can now search for woman, not the authority to demand one.

hmm the virtual reality program sounds the most plausible, but it still feels like that can't be near the feeling of a real avatar...

yeah that might be how she ment it...but there's still the fact that Grace telling Jake that Tsu'Tey and Neytiri are suppose to become a mated pair. I wonder where she got that information...

Jake probably have different values cause he's raised as a human with human values (that of course differ in different cultures)

Yeah, SUPPOSED to. This doesn't say they HAVE to by Clan obligation. Its quite obvious Neytiri doesn't love Tsu'tey. Jake is Shmexier to Neytiri, so, Jake Win <33

Is there anything that confirms the avatars didn't start growing on Earth, then "fully matured on the flight out" being that they were in some kind of infantile state when loaded into the ISV? If that is true, then one could link to (but not do anything with) a very immature avatar. If this is true, I would imagine that the link-time is used for tuning the connection. However, then what would explain Jake's zero-hours-logged and epic avatar usage?

Well Jake was given the job just as they were shipping out for Pandora, I'm sure there wasn't enough time to get him training for it. Jake is Tommy's genetic twin, so its quite possible that because Tommy was already 100% tuned to the Avatar, and Jake is identical to Tommy, that it didn't require any more. Maybe you could link with an immature Avatar, but its also possible that the brain isn't fully developed and therefore impossible to link to one.
My two cents <33

Simulations.
My interpretation of this is that anyone could choose someone else as their mate, whether the person who chooses is male or female. It's mentioned elsewhere that choosing the right person can take years. Neytiri just mentioned it that night for the same reason she took him to the Tree of Voices to - she wanted him to choose her.
I would also guess that the person who is chosen has a say in it, if they were unwilling then the mating before Eywa would most likely fail (again, using survival guide etc as a source here)

The Survival Guide DOES rock. Its a great thing...

As others have said, it's possible there are simulations on Earth, just like there are simulations for plane drivers or astronauts.

Yeah, I guess so.

On the mate subject (I have read a lot about it haha the Na'vi way I mean) in the Activist Survival guide Says that when an appropriate mate has been selected (which could take years) so I'm guessing that when it says years, it's a connection that the two will have for each other. They are ones who are very in touch wih their surroundings so I'm pretty sure the woman has a say in t as well... and as for Neytiri being mated wih Tsu'tsy it's because the spiritual leader and clan leader has to be a mated pair and they were both chosen for one of those parts

I took the meaning for Neytiri and Tsu'tey being paired was for the fact that she will be the next interpreter of Eywa and Tsu'tey the next clan leader. Just the way it goes with Na'vi I suppose.

For the others I felt it to be more of a connection they feel, like when people date here only slightly different. They then "choose" each other and mate for life.

On the link, I assume like others have said that it was some sort of simulation. Obviously not going into the Avatar bodies because they were doing body function checks yet after the first day they slept in a hut leading me to believe that after the initial check it was just link up and go.

This all makes sense, and is how I hoped it would be

"That's a gorgeous brain."