We don't normally get very excitied about a decimal point upgrade but the Rails community seems very pleased with the extra speed provided by Rails 3.0.3.

According to the Ruby on Rails weblog:

Rails 3.0.3 includes a much faster version of Active Record that reclaims the performance lost when we went from Rails 2.3.x to 3.x and then some. Aaron Patterson has done a phenomenal job benchmarking, tweaking, and tuning the ARel engine that underpins Active Record 3 and the result is The Snappy.

Back in an August news item, Rails 3.0 Release Candidate,  we reported that a key improvement for Rails 3 was speed:

The main emphasis of the release seems to be speed improvements.  As with all interpreted languages, speed is an issue and the Rails framework is quite demanding. It is claimed that speed is good across all aspects of operation apart from Active Record, and it is hoped that will be fixed before the final release.

In addition there's "a truckload of minor fixes" and it is a drop-in replacement for Rails 3.0 - so no need to worry about having to make any changes to your code.

Further reading:

Rails 3.0 Released

Rails 3.0 Release Candidate