Although bundle exec rake db:migrate is probably the single biggest killer feature in Rails, there is a lot more to rake.
Rails offers several rake tasks to help with everyday project management, like redoing a migration because you changed your mind on one of the columns, clearing your log files because they get so big, and listing out the TODOs and FIXMEs.
What's even more awesome that all that is that you can create your own rake tasks. Got a tedious command-line process? Write a rake task for it!