Here's a post from the Varnish Software blog discussing how web site speed affects online businesses. One of the studies they use is four years old, but I think the numbers they show beautifully illustrate why speed matters:
Shoppers (in 2009) often abandoned websites that took more than three seconds to load. (How quickly might they abandon a site in 2013? What about from a mobile device?)
A one second delay in resulted in 11% fewer page views and a 16% decrease in customer satisfaction.
Now, I'm not going to say that LiteSpeed is the answer and Varnish isn't. For the most part, we do different things. (LiteSpeed does, of course, have its own cache service, available starting with 2-CPU licenses, but we haven't seen a good benchmark comparison of the two of them for a while.) If you're looking for an easy way to keep customers on your website (or help your users keep customers on their sites), you might want to give LiteSpeed a go. With Apache drop in compatibility, you could have your server on LiteSpeed Web Server in 15 minutes. In recent benchmarks, we've shown LiteSpeed to be much faster than Nginx, and you won't have to learn a whole new system or ditch your control panel. LSWS will both speed up your server processes and lower your memory usage, leaving more room for those other processes that cause server load (like PHP and MySQL). With a 30 day money back guarantee (and 15 day trial licenses), what do you have to lose?
Of course, maybe I'm preaching to the choir.