RCN Cable and HTDV

Seems like RCN in the Masschusetts area is ready for HDTV starting May 15th. There will be new converter boxes etc. Channels inlude: AbcNbc, Fox, PBS, Discovery hd, Hdnet, Hdnet movies, Hbo hd, Showtime hd, Espn hd. Will be additional cost for these. This is the way to get a converter box with better output than composite video?

Some more info as time goes by. Here is a FAQ on the Motorola 5100 that RCN seems to be using. There is also talk that the non HD channels output quality is poor and Motorola is working on it.