sadly, Sprints marketing team was rather good at being vague in the commercials and adverts for this feature.
if you watch the commercials or read the prints carefully--it never states that it will stream online content from the phone to a television. really, it's just for content stored on your SD card (ie recorded videos and such)--
as far as MotoDroid's go, a fellow named DroidGuy (i believe) has created a ROM feature (for X's, i believe) that will allow anything on your screen to be shown on the tv (streaming content, webpages, anything)--but he has yet to incorporate any variation for Evo. alot of people have talked about getting $ together to pay him to develop such.
i really hope someone does develop something to enable this--i'd love to actually use the HDMI port for something instead of just knowing it's there. but, i suppose, DLNA is the next best thing...but i'm not going to GalaxyS's for that--no thank you