After using my Philips DVP3888 for over a year, here are some of the experiences of the same. I feel most other similarly modelled players will also have such issues, but do post if there are changes. Most of these are half-baked laymen experience, so do NOT expect any technical stuff (unless typed in by accident)

1. It supports DivX, Xvid (i havent tried all variants in that though).
2. Any video with resolution higher than 720p (width) does not show video although audio plays
3. MP4 files are considered as mp3 files and no video is displayed
4. Any movie which is bigger than 1.2Gb plays plays only till that time when the file size reaches 1.2Gb... that is, if the movie length is say, 90 minutes, and the file size is 1.3Gb, then the movie stops playsing approximately around the 75 minute mark. I had to split the files into smaller sized chunks (I use FormatFactory for this)

5. If your pen drive becomes too fragmented, then for video files, I have seen two cases
--> 5.1 The audio lags the video (or)
--> 5.2 The audio and video slows down pretty badly that a female voice will sound like a male

The same video worked fine after I defragmented the pen drive.

6. Photo loading is pretty slow
7. To load a photo fast, I had to press the next photo button. In this case, the current photo loads up fast (i dont know how it works, but yes, it works).. but soon the next photo starts to fill in top-down.
8. In my player, if mp3 files are present in the pen drive, then the first folder it encounters start to play the moment the drive is loaded.
9. I think it supports usb HUB based devices also. Cos, I once used a multi-card reader and used a CF card to view photos and videos and it worked.