would like to say i have just started using audacity and though i am finding it full of excelent filters and easy to use  . you still really need to be a profesional to use it .  as you have to apply filters and thus ajust settings prior to playback, this means you need to know in advance the db amplification or mS delay times of echo you need to use.
It would be most useful if you can apply and change settings during playback so that you can hear (at least some of the time) the changes as you apply them. (excelent for re -mixing/mastering).
presently I am manually (so boreing) removing clicks from my digitised vinyl as havent found anything good enough to automate the job yet.
audacity is looking good ...so keep up the good work.