In the course of trying to figure out why the heck SL is so slow one might develop the desire to test how fast their internent connection really is.
There are lots of sites for doing that but they measure TCP/IP bandwidth, not UDP, which is what SL uses.
I came across a UDP speed tester lately.
It's called TPTest, at http://tptest.sourceforge.net/
The executable files are available at http://sourceforge.net/project/showfiles.php?group_id=55924 .
Hope this benefits someone.