In my personal opinion, they are cheap but not as good as the other good brands in the market.
1. For most of the tables it is difficult to get the Hardware and software support.
2. They do not provide regular OS updates.
3. The hardware specification is not standard, For ex: most of them are not even 1GHz CPU speed and have a very low level of RAM which is necessary to run media rich applications.
4. Not compatible with most of the devices present in the market.(Bluetooth and USB)
Anyways the price of all the branded once will also come down soon and would be in reach for everyone.
I personally own an Archos 5 Internet Tablet 16GB version, has ANDROID 2.0. It is able to play all the media format i have, has an inbuilt GPS and FM, with the help of its DOC i can connect it to my LCD TV as well, in all its my portable multimedia gadget.