As far as I can see, throughout this thread the performance benefits of single page apps are touted as being fantastic, making it worthwhile to use the new technology etc.
When has performing operations efficiently ever been the domain of the web? Websites in my experience have the worst performance of almost any software I use! I've seen developers cite 200ms or longer to load a page as being a good benchmark - that seems pretty awful to me.
If getting this tiny performance improvement (which often results in poorer performance on the first load (not ideal for many)) is so critical, why do the same developers not invest in writing more performant server apps? Yes, often the database is a bottleneck, but these problems can in general be worked around (either by use of faster queries or caching etc).
Why attempt to get a small performance benefit by saving 30-odd kB of HTML on each page load (static and so essentially free for the server), when one could get a much larger performance benefit by optimising the backend?
Almost all serious sites will still see their page load being limited by the time it takes to produce the page. It's possible to write really fast websites (try http://forum.dlang.org/) but no one seems to do it :(
If anything but almost all of your website is static, you won't be saving all that much time.