Unless I'm somehow the exception, when using the topics view, which is all I use, it is as though subgroups do not exist.  There is no way when you land on the topics page to know that there are subgroups.  Even if it were a single button at the top that read Subgroups and somehow gave an indication as to whether or not there were new messages "hiding" there would be a major improvement.

To each his or her own on the final design, and that could be fleshed out.  I'd rather see the top list, with each subgroup having a single line that clearly indicates its current "new message" status if you're logged in.  I'm perfectly OK with alternatives that require a "click to check" with some sort of clear, fixed indicator on the main messages/topics page.  If you don't have that then we're back to square one, particularly since the far more logical "land on messages/topics page" default has been implemented.   I am subscribed to a number of subgroups, most of which I have e-mail notification on for because they get little traffic, but if twenty more were created for a given group I'd be really unlikely at this point to ever know that they were there if they were not announced.

I consider subgroups to be part and parcel of a group, but just a way to guide message creation in a more structured way.  As a general rule, though few have them here, I like any group to have a "chat" group that allows members to post whatever they please (within the realm of common decency).  I have yet to be a member of any group where, at one point or another, members don't post something that's off-topic because they want to solicit answers from people they think might have them who they interact with regularly on the actual central topic of a group.
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Brian

A lot of what appears to be progress is just so much technological rococo.  ~ Bill Gray