WordPress 2.0 isn’t out yet, but every day that I spend on the #wordpress IRC channel, I see this question go by at least once:
What is new in WordPress 2.0 from 1.5?
Wouldn’t you like to know?
One important note before we begin: Many of the changes in WordPress from 1.5 to 2.0 are under the hood. They are things that you’re not going to notice unless you are developer. There are some features that casual users will notice that are significant, but (in my opinion) most of the real change has happened where most people won’t see.
As a result, there is a fundamental thing to understand here. What often looks like catering to plugin developers is actually of benefit to common users, because with the enhanced capabilities of the underlying engine it becomes possible to make better extensions faster than we could before. The underlying engine has been made to work better. There have been times while doing contract work on 1.5.x installations where two days of work were necessary to accomplish something that I could have done in 1.6 (now 2.0) in about 10 minutes. Seriously.
There has been a lot of talk in the WP scene about feature bloat, and it’s my own opinion that certain aspects of 2.0 are wildly overrated for what they do, but from an underlying technology standpoint, WordPress 2.0 is incredibly superior to the 1.5 codebase.
So if you don’t want to upgrade because you don’t think that 2.0 offers you anything, just wait a couple months until the really fun plugins start appearing.
Enough said on that. On with the new features list, which is by no means comprehensive: