I performed some new tests and I totally eliminated DOM modifications (HTML 5 canvas use) which I realized they were slowing the whole polling process down. Surprisingly I got an almost constant 20 message per second! Then I read Mr Crivelli's post and understood why it was stopping at 20..

I performed a test which basically involved a JavaScript loop making calls at different timescales. I could scale up to 50 requests per second while still getting a server response without delays (on a local network). If I added more request per second I started to get delays and hence replies from server started getting mixed and not in order.

I am sure lightstreamer can scale up this much with polling as well and I will try the javascript library modification you suggested to test this

Thanks a lot, your replies were very helpful.