Android in my opinion is not the way to go on these devices - but I like loading the applications and messing around.
There could be numerous issues - the older avi containers do have an issue on Android that I know off where the chipset
doesn't like the container. MP4, MKV files should not be a problem - I have no issues on my box, however the 24P issue is there and I can see it! HD content seems to perform better than SD content IMHO. On Android the software and not the GPU does most of the work. That's the problem.
Scraping media for meta at e.g caching is a way of obtaining the synopsis, genre, year as you said via a scraper application. It seems that what your gallery app did just that and filled up your devices internal memory. The device becomes sluggish and tends to lag more. I have no video nor audio lag (currently) but I'm using a hard wired LAN connection on XBMC for Linux.
Setup is as follows:
8 Gig MicroSD card - with user data for XBMC (not to full up internal device)
TV: LG55LA6210
Usb: 2 TB Seagate
Network: Wired, 100 mob full duplex
I don't do apps, as I believe a dedicated device is better for somethings however I want to look into the Rom Collection Browser to play a few old time fave's.

You can also check your CPU and memory utilization via Xbmc. Try disabling add-ons, choose stero output if you can and changing the video output to 720p. See if it makes a difference.
I played a 25 Gig ISO over the network last night and the unit bombed out in 15 minutes.
Impressed :twisted: