Hi Chris,
I can answer most of your questions as I've been looking into this issue for about the past year...
pagan: Are the Data plans from the normal Kordia's Extend or the Kordia's Extend lite version?
The Xtencity plans from Xnet are based on Kordia's Extend Lite plans as follows:
SPEED
DATA
COST (per month incl. GST)
256k/128k
3Gig
$99.00
512k/128k
5Gig
$125.00
512k/256k
5Gig
$129.00
1M/340k
10Gig
$179.00
$1.00 per Gigabyte when usage exceeds cap
In order to connect via any of these plans, your router needs to be set for PPPoE whereas the earlier Extend plans used a VLAN connection.
pagan: And what is the differance if its the lite version?
The "Lite" version has no Committed Information Rate (CIR) unlike the earlier Extend plans. However, because Kordia's Extend network only has 2000 customers nationwide, this is unlikely to make any difference!
Having no CIR means that you are contending for the available bandwidth with other users on your particular "Shelf" of equipment according to Kordia. At the transmitter site I am connected to, I am the only customer using my equipment shelf. So, the lack of CIR will make no difference at all.
If you had a lot of neighbours connected to Kordia Extend (pretty unlikely anytime soon...) who were all doing large downloads or sending large e-mail attachments at once, that is the only time you would possibly notice any degradation in speed.
pagan: Also is local traffic free?
By "Local Traffic" I guess you are referring to traffic within NZ i.e. National traffic. No, this won't be free. However, traffic within Xnet's network e.g. VFX traffic and POP3/SMTP e-mail traffic WILL be free. Keep in mind though, that Xnet's traffic charges will be extremely cheap compared to any of the other ISPs who offer Extend plans:
ICONZ $130 per GB
InsPire.Net $120 per GB
Xtra Wireless $50 per GB
...
Xnet Xtencity $1 per GB !!!
There's not really too much to worry about if you go over your cap

Now, here's a question for Maverick:
The earlier Press Release concerning Xnet Xtend (as it was called then) referred to 10 Hours per month of free calls to any NZ Landline. The new Xnet Xtencity page: http://www.xnet.co.nz/xtencity/ says 6000 Minutes i.e. 100 Hours...
Which is correct?