I used Joomla way back in the day but I don't see any reason why you couldn't... you may, though, run into problems with Joomla's global vairables as you would be using a "set" template for your DA stuff - even though it would be styled the same.
I have heard and read that Adobe's DW CS5 will start have native support for site engines like Drupal, Joomla, etc... it will be interesting if that comes to fruitiion. I can see leveraging WA products to make some really nice stuff with those frameworks.
Cheers,
Brian