Over last weekend ONDA released the v0.8 firmware for the Vi40 R4.0.3 platform. In the release note, it is stated that this firmware makes it more stable and includes some Google Apps, such as Market.
The upgrade itself is quite easy and fast --- it takes about 15mins.
Backup using TB or Wandoujia.
The internal sdcard will be reset by the upgrade so make sure to make a copy of it as well.
You can find the firmware here:ONDA
1. It seems to be more responsive
2. The Google apps work well, such as Market/Reader/GMail/G+/Docs/