how it's been before:
i install a plugin. a tiny scrap of code i put into my sidebar.php, wham, there it is, working. i can customize my sidebar as i want, putting in mini loops, customized category listings, etc.
how it seems to be with widgets:
i no longer have control of my sidebar. instead, anything i want to be in my sidebar HAS to be a widget, which means anything i want to put in my sidebar i have to turn into a widget. this seems like a lot more work for me.
it's quite possible, however, that i'm misunderstanding, that instead it is possible to have customize your sidebar.php file, and use widgets at the same time.