I have to say that I'm not pleased with the render times using templated controls for topic and post lists, but I could be over-reacting. On one hand, I'm looking at .2 seconds, but for someone running a site without a ton of traffic, that shouldn't even matter. For my own sites I think I want it to be below .1, which is kind of the benchmark I use for everything else I have running right now, and I think to do that I'll need to resort to custom controls. So I might introduce two versions of the UI, one for tweak monkeys and one built for all-out performance that isn't as easy to hack.
I had a discussion about the importance of creating a Usenet-style UI for threads, and I wonder how important that really is. When you discuss it with geeks, they stand up and say, "oh yeah, I want that." When you discuss it with everyone else, they say, "Usewhat?" It's so weird how the Internet has been with us for such a relatively short period of time, yet the experience gap is enormous, especially from thirty-somethings to early twenty-somethings.