They are all quite similar, though some claim to have more internal memory than others (4GB vs 2GB). They claim to support sdcards up to 32GB.
The screens are said to be 7 inches diagonally.
Almost without exception they have no reserve price, but if you bid you find there is always an auto-bid set up to beat yours.....
I'm assuming this is the vendor in various guises gaming the system to get the price up to a point s/he is happy to sell the item at.
Whether the auctions are being conducted in an ethical manner or not, the Buy Now price is fair enough for a device with those spec.
They are wifi only (b/g/n).
They support headsets and have built-in mics....but it isn't clear they support a headset with a mic.
They do not appear to support Bluetooth.
CPUs are about 600MHz and RAM is 128MB.
Android "v1.7" is said to be the OS, but with a firmware revision of v1.6......so presumably someone has modded it (or not)...and made a custom version.....or not.
Have a look. I might buy one just see what they are like. An android tablet device with a 7" touch screen for $249 isn't unattractive.