I bought the ug802+ which includes a better antenna, but is only 2GB internal storage, with microsd slot, about 5-6 months ago.
XBMC released a new version which supports hardware 1080p video decoding about 3 weeks ago.
Astro isn't great for stability, try es file explorer.
You can typically upgrade these units by copying the firmware to the internal sd card and rename the firmware update.img
Given the feature sets, it appears that most of there units are off the shelf oem devices with a custom case wrapped around them. Look around.