Upgrading a Rails 2 App to Rails 3

Dive in now. I am using Rails 3 for our new project and it works perfectly fine. There are no real reasons to spend effort on building something on Rails 2.3 now. Especially, given that Rails 3 has significant improvements and is a pleasure to work with.

I've heard they're targeting RailsConf - but it's really anyone's guess. The frequency of commits doesn't seem to be decreasing.

Dive in, the water's fine! You may experience a few bumps along the way, but there are a lot of people already in the water ready to help you out. There are already production apps running Rails 3--just don't use it for anything mission critical.

Nope, but all of these people do: http://railsplugins.org/plugins/161-paperclip

Railsplugins.org has been an invaluable resource for me to figure out what's happening with plugin and gem compatibility.

Now if they just added a JSON layer so I could automate the process of checking my projects' gems...

Paperclip w/ Rails 3 beta is kind of a moving target right now. As of yesterday, the rails3 branch of the main repo wasn't working in my only Rails 3 app, but this fork works for me: http://github.com/enable/paperclip/tree/rails3

I have, and it works.

I can confirm that Paperclip does work with Rails 3. Some recent merges and updates broke it for awhile, but I think things are back to normal now. (If not, a pre-March fork of the rails3 branch will do in a pinch.)