What with the site overhaul is there now any facility to be notified ( email, or even just an inbox message) of replies to forums threads, either a thread I started or one I'm participating in?

If you are using firefox for your browser and have installed 'greasemonkey', go to this site.

http://bigdogghouse.com/RHP/

You will find a variety of scripts that enhance the RHP site.
One of them does exactly what you are asking about.

These are excellent, thank you.