[nu11ptr]

I did not work on the kernel itself, but wrote NDIS IM kernel drivers (a shim between NIC driver and TCP/IP - like a firewall or load balancer). I found it lots of fun personally. Back in the day I recall using Windbg and later SoftIce for debugging, so when you got stuck there was lots of rebooting to get into a debug session and then careful stepping which could be tedious. It was very challenging, but rewarding and every cycle/instruction counts and every memory allocation had to be carefully allocated from paged or non-paged (never swapped out) pool. I specifically recall you could only call certain functions/syscalls at certain IRQL levels or the kernel would bluescreen, so you always had to know which IRQL level you were being run at. This was 20 years ago so I'm sure much has changed (and probably much hasn't).