I’ve been a Wireshark devotee for probably a decade. I’m sure I’ll continue to be a huge fan for everyday use. I had heard stories about Microsoft’s Network Monitor being awesome a few years ago at GDC, but hadn’t actually tried it out until now.
I have to say, for developing custom protocol parsers (for debugging the mutliplayer game you’re working on, for example), it wins hands down. I might never write another Wireshark dissector again.