Lately I seem to have noticed a trend amongst some RoR developers, that is using RubyEE/Passenger/Apache type setups during their development process.
Besides the obvious "use what your clients use" idea, do these technologies enhance the development environment in any way compared to what the vanilla mongrel stack gives you ?
Ruby Enterprise Edition uses less memory than vanilla Ruby because of its improved garbage collector. May be that's something you also want to take advantage of in development.
As Passenger is running all the time you don't have to mess about stopping and starting Mongrel. Simply open your application's URL. If you're using Mac OS X there's even a handy preference pane which makes configuring Passenger to serve a Rails application a mere drag and drop away. It also lets you easily test your app in production mode.
Yes, especially using the same database. It allows you to flush out errors such as rand() vs random() and also lets you use sql specific to that database (e.g. ilike/functions/triggers/views, etc).