Tablets designed to run Windows often will run Linux pretty easily, you're basically looking at a laptop with a touchscreen and no keyboard, so the same gotchas apply.
Android tablets running generic Linux is a different matter, because there are many ways you can wire up a system-on-chip to its peripherals and not all of them "auto-probeable" like what you see on x86 platforms. (e.g. on I²C busses, the best you can do is poke an address and see if you get an ACK but you have no idea what you just spoke to. SPI is even worse.)
However, if the manufacturer made their kernel source tree available (and they should!), people can often use that to cobble together an environment for running an alternate Linux OS.
