Human perception on latency....

http://blog.benstrong.com/2010/11/google-and-microsoft-cheat-on-slow.html and http://books.google.com/books?id=aU0MR-MA-BMC&pg=PA292#v=onepage&q&f=false    show to me that, by experiments, when latency is under or roughly equal to 150-160 miliseconds, human sense can not feels or sees that. Good to know.... so one just need to make sure computation result is shown under 150 ms and we shall say "Dear Lord, it's magically appears" :)