It would be great if there were more hobby OS resources targetting something other than X86. It is common and everything, but all the bootstrapping and device cruft involved isn't something you should need to get in your head, and 386 assembly by itself is terribly frustrating and obtuse to write by hand. I think most people might be better off starting out with a RISC microcontroller. There isn't nearly as much bullshit involved between getting a running kernel and talking some simple serial, and you can get an instruction set reference, assembler manual, and processor datasheet that will tell you everything you need to know. And it's easy to have fun hardware hacking that way too, making your own peripherals and such.