First off, I'm totally fine with the TechTalk transition. I was never a big fan of the email format, but from the reaction to the transition, it looks like a lot of people liked it.
That said, I think one advantage that TT had, was that you could easily scan the messages and decide for yourself if there was something you were interested in. The current format of the forum has 25 categories, and I think that it requires too much clicking to see what is happening in each of them. I'm a fan of HBD's Brews & Views where almost all activity happens in the main forum. It also has a very powerful search engine and a huge archive of valuable information that is really easy to navigate. I think one advantage to fewer categories is that I would most likely never click on the "Extract and Partial Mash" category since I'm an all grain brewer, but I'm sure there would be threads in that category that would interest me. I would think that the All Grain, Extract/PM, Kegging, Yeast, Ingredients, Equipment and Recipes categories could all be combined into one general category and most of the users would be interested in all of them. In the last 24 hours, all of those topics had a total of 33 threads with activity. That seems pretty reasonable for one general brewing forum. If at some point it turns out that too much activity is happening on one of those subjects and it is clogging up the forum, then it could be broken out again.
If reducing the number of categories isn't an option, then perhaps there would be a way to look up recent threads with activity. I see that there is a "Recent Posts" link at the bottom of the page, but if you aren't familiar with the subject of the thread, then seeing a reply out of context isn't very helpful. I believe it would be more helpful if there was a way to look up recently active threads with just the titles and number of replies showing up.
I'm sure a lot of thought went into the current format, and I'm not trying to knock it in any way, I just thought I'd give my thoughts. Thanks for considering them, and happy brewing!