A few functions might've been renamed. I think the only major thing that might impact your code is the expanded channel system. A player can be in more than one channel now, so a lot of functions now require a channelID.
Also, the OnNetworkConnect, OnJoinChannel, etc messages no longer fire automatically. You have to subscribe to these events manually through TNManager. Just do this in each script's Start (if it needs to).
Other than that I think it's mostly improvements: ridiculously thorough serialization that supports literally everything, no longer having to register RCCs, full singleplayer support, and a bunch of other things.
You can check the changelog here:
http://www.tasharen.com/forum/index.php?topic=2650.msg61799#msg61799And it might be a good idea to skim through the (new) tutorials:
http://www.tasharen.com/forum/index.php?topic=13953.0