I have the same issue with not seeing newly added files via streaming. Here is what I added in a different post:
I have my iMac set to sync to my Apple TV running version 2.0.
I only 'sync' the photos from the iMac to the ATV.
'My TV Shows' lists all the TV Shows I have on the iMac, so obviously they are being 'streamed' to the ATV, which is cool. I assume what happens when the ATV boots is it reads the iTunes XML for the machine it is 'synced' to, and populates the appropriate listings.
Here are the problems I have experienced around this though:
1) If I add a new TV show, or episode, to the iMac, it does NOT appear in ATV without performing a sync at iTunes on the iMac. I have waited up to 30 minutes to see if it would auto sync, and it never happened. I assume this has happened as ATV has read the iTunes xml once, and doesn't read it again unless a sync is forced from the 'synced' iTunes.
2) After watching new episode on the ATV, the blue dot disappears next to the episode, but when I move up the menu structure to the list of shows, the show still shows as having a new episode, even though I just watched it. Again, a resync is required at the iMac to sort it out.
3) Related to point 2, when I watch a show on the ATV, the iMac still displays the show as unwatched, even though it has been. Obviously a sync from iTunes fixes it.
Shouldn't the iMac and ATV periodically sync with one another, or do I have to perform random manual syncs throughout the day? Seems a bit silly.