FWIW, I am also a (long time) Comcast customer.
Certain Comcast channel offerings *will* require their HD tuner or HD DVR box rental, not simply the converter (digital transition) box. However what you might first try is to re-scan the channels when connecting directly. It's possible a few more may come in correctly given your Aquos likely has a built-in QAM tuner for unencrypted content. Most of the HD stuff still won't be available w/o box rental though. That's how they pay the bills.
Hey there, I have a sharp aquos LCD T.V, and what I am wondering is that when I plug cable directly from T.V to my wall I get the major network channels in HD. The problem is I don't get any of the other channels like discovery, or comedy central. When I use the box Comcast provided for the digital transition I lose all the HD channels, but I get every chanel. Is there anyway I can watch my t.v without the comcast box but still get all the other channels? Thanks for the help.
By the way this is the box http://hdtv.biz-news.com/news/en_US/2009/04/18/0002/comcast-extending-all-digital-push-in-boston-and-atlanta