Wow! Thanks Kerry - that's a lot of info to dig through!
From the general gist of things though, it seems to me that most are of the opinion that you need to vlax-release those objects created by vla-getInterface.. vlax-get-or-create... vlax-create, but vlax-get-acad-object will take care of itself, as its from within AutoCAD.
But, as you say, I suppose it depends who you talk to...
Thanks for your time,
Lee