The problem with "Show new replies to your posts." is that the list keeps growing. Even topics I posted in years ago still keep popping up. When I started on Bitcointalk, I used it a lot. Until I read this:
Yeah, it's true. It's a bit annoying when significant part of topics that you can see there is spam megathreads. So, time from time I click mark messages as read to see less irrelevant topics.
I know that using Watchlist is more convenient, but for me it's a bit difficult to change old habbits.