You'd use WinDBG today. It allows you to do remote kernel debugging over a network. This also includes running Windows in a virtual machine, and debugging it through the private network connection.
FireWire is also still used to dump out kernel debug.
Shouldn't IOMMUs block that these days?
SoftIce predates me, but when I was doing filesystem filter driver work, the tool of choice was WinDbg. Been out of the trade for a bit, but it looks to still be in use. We had it set up between a couple of VMs on VMware.