It matters in some contexts.

For quick scripts that you invoke from the console, it's painful to wait a couple of seconds just to see if it does something.

For web servers, if you're using something like Google's App Engine which starts VM instances as needed, or stops them when there's no traffic, users have experienced what is called a "loading requests" ... which is basically a very slow request or requests throwing DeadlineExceededExceptions.

That's because the startup time of the runtime is very slow, especially when you have big dependencies like JRuby ... see this blog post for instance ... http://googleappengine.blogspot.com/2009/12/request-performa...

One case that comes to mind - quite often when I do unit-testing in JRuby, and run a single test from the command-line, the test will take 1sec with JRuby vs almost nothing in regular Ruby.

So I find myself running the individual test using MRI Ruby while developing, although the whole test run will be done with JRuby in the end, just because of startup time.

Ok - so you've got a script that runs in ½s, but it integrates with some .net stuff, so you run it under ironpython. Instead of getting the result straight away, you have to wait 3s (startup + run). It will be at least annoying if you rely on that script many times during the day.

the scala and clojure folks have spent a lot of bandwidth discussing:

http://groups.google.com/group/clojure/browse_frm/thread/33f...

http://stackoverflow.com/questions/1316056/how-to-reduce-sca...

http://www.assembla.com/spaces/clojure/tickets/81-GC--Issue-...

http://groups.google.com/group/clojure/browse_thread/thread/...

I use Python quite a lot before I try Scala (on JVM). I have to say the slow Scala interpreter startup (due to JVM, again) really pisses me off for scripting in Scala (otherwise it's a nice language for scripting).

It's stupid to have to wait >2 secs from pressing F5 to seeing the results of your code. Maybe not for a Java programmer, but if you're used to instant results from CPython it's annoying.

If memory serves, this was important for cgi scripting -- where a new page hit launched some python code (and hence a new interpreter process).

Mercurial, and the others of that ilk.