Please take a few minutes to visit the official Nirvana forum over at rcgroups.com - it is by far the best resource for anything to do with the Nirvana. There are over 200,000 views on this thread and is very likely the most active sailboat thread out there.
The short answer is the newest version of the Nirvana ll is pretty much the same as the previous versions accept for the radio update.
Check out sailrc.com for all the details on the new boats. Steve Lang is the owner of sailrc.com and is the Master Distributor for the Nirvana in the Americas. Super nice guy, life long sailor and knows his stuff!
Here is a link to the Nirvana forum for you : http://www.rcgroups.com/forums/showthread.php?t=794969
These boats are time tested and continue to grow in popularity. Very solid engineering and design has gone into these boats which has produced a boat that is elegantly simple in design, which makes them very easy for the novice to get started with, but complex enough to keep the interests of seasoned sailors for years.
Check out both sailrc.com and the Nirvana forum, I am sure you will find them of interest. I posted a few photos of Nirvana's owned by forum members - many of us personalize ours, many don't and sail um stock and havejust as much fun!Either way, these are good choices and really have nodown side that I have seen. Enjoy.