I don't see LT as viable on the English Wikipedia and where its use is intended for the following reasons:
Did I mention it's slow, laggy and ugly?
Yes it is, And there is requests every so often on the VP:* to get a decent system to replace them.
It doesn't look that bad ((in it's current state) and I quiet like it) but I haven't paid that much attention to the redesign theme ideas.
I would certainly love a linear discussion format on the VP, that way people won't get confused as to who's talking to who given how long discussions can become. You don't think this current design is ugly as fuck, because the last thing I'd want is to go to the VPs and have a chunky, laggy, waste of space messaging system, no rudeness intended at you or the developers but this design and its speed is just not viable for enwiki, at all.
I agree with some of your observations:
1) It's important to find a way to load faster - particularly the top part of the page / the first threads. LQT does not load quickly on any of my current machines, even for a talk page this size.
2) You can save a few pixels with a 1-px border, 2px less padding. You can save 1.5 lines (on most displays) by floating the sig and reply/parent/more options to the right of the comment. In the v3 designs, you can move the Reply/Comment/Edit Summary buttons up into the header of that thread/node.
3) I'm not a fan of the current design. However the New design is scrumptious!
4) Talk pages are indeed forums, they simply need to stay on topic. You may be misinterpreting that section.
