Last week I got my DDP's N900 and since I still have my Summit's device I haven't played with it much. I wish Marcin Juszkiewicz wrote his DDP device checklist earlier. I got this nasty bug 6823 "media player won't play any video files now (.avi) divx / xvid". I tried all files, even the default "Nokia N900" and "9". Since Mplayer plays all video files, this is a software fault, not hardware issue. But still it's frustrating and I'm waiting for any bug activity.
So my point is, all people who got their devices, please check for video playback in media player. And vote for the bug if necessary.
