Has Lt been tested in high traffic environments and with huge watch lists? I am an admin in two high traffic project and have a watch list with 3500 entries. The "new messages" page is useless under these conditions. Furthermore LT is unusable in high traffic environments: Try finding the three new messages in a tree of 400 or more contributions. Or worse, the 26 new messages in a 1600 entries tree. And yes discussions like that happen, my fav example are discussions over notability criteria on deWP. On traditional wiki-style talk pages I can call a diff over 26, 65 or in extreme cases 220 versions and scroll down. I then have to read the new stuff in the small font or zoom my monitor display, but it works. Perfectly fine, once I understood how things work.
Topic on Talk:LiquidThreads 3.0/Design
Diffs (was: Huge watchlist and high traffic environments)
Yes, diffs are useful. Their problem is that you don't easily see the context. Perhaps we need LQT to allow collapsing of already read messages in a thread, beside highlighting of unread messages.
We'll be working on New Messages in a design meeting in the coming days.