I wanted to mention that in IE 8, Microsoft has introduced a new Comet
technology called WebSlices. The closest thing to it is Long Polling
Comet but there are several enhancements to Long Polling. I've blogged
about the differences here:
In the beta of our Dynamic Mashup Server-- which uses embedded
Grizzly-- we introduced support for WebSlices. Unlike Grizzly which is
both a Comet and non-Comet web server, I think that Comet vendors who
do not support non-Comet access will have reduced market acceptance.