To help with the transition [to Rails4], over the next 31 days, we are going to be releasing a series of blog posts going over everything you will need to know about Rails 4 for an effortless upgrade.

Covers amongst others:

• caching gem extraction
• etags
• strong parameters
• observers gem extraction
• session store gem extraction
• html5 form input helpers
• ruby 1.9.3 required
• russian doll caching
• ActiveRecord news
• much improved Postgres support (e.g., hstore)
• streaming
• Rails4 upgrade guide

Link: [Rails 4 Countdown to 2013

The Remarkable Labs Blog]1 via blog.remarkablelabs.com