I takes nothing to upgrade. Most templates only have aboput 5 diffrent templates so open up what ever you use get the 2x template and the new 3x template and start convreting. It take ya a day and your done and your upgraded.
The CSS is not hard to fill back out and hacks, well all the good ones are there. Like quick reply, today/yesterday/profile pic/user rating system/rank images the admincp, mod cp and user cp all are 100x better. The code is 100x better. A dubug mode that give 1000000x better info then microstats ever did hell I could type for a week on how much better it is.
It is more then definatly worht it and even in beta. I have only seen a few minor bugs and that was in beta 3. And if you do the upgrade now not all to much to worry about late