They are good for the money and a good option if your wanting to dabble but for serious tablet use you get a lot more for the money with the dell, toshiba, etc. Windows tablets.
Almost all Windows tablets currently use a limited range of internals as far as the mainboard and SoC goes (and range of hardware specs) so in that regard you won't get a cheap tablet with cheap buggy hardware, etc. as happens way to often with generic android tablets - the core of the tablet should be reasonably robust and reliable (Windows 8 charging bugs aside).
The screens are ok but nothing amazing, the LinX ones tend to be decently sharp but colours are a bit muted overall.
Chassis doesn't feel or look cheap cheap but its run of the mill moulded plastic and doesn't feel quite as substantial or as well crafted as some of the more expensive ones.
Battery isn't as good as the more expensive ones but pretty much on par with generic android tablets, though tends to run down a bit quicker while in sleep mode than the dells and toshiba windows tablets (my gut instinct is the wifi isn't going into a proper lower powered mode).
Cooling doesn't seem to be as good - under heavy use the CPU will eventually thermal throttle to 300-500MHz until it cools down whereas the more expensive ones typically have better cooling and you'll struggle to make them thermal throttle under all but synthetic load torture tests.
EDIT: I would second what POB said - unless you need ultra portability/have a specific use in mind go for the 8" over the 7" if your going sub 10" as the increase in usability is huge especially when dealing with the onscreen keyboard.