When you install eZ publish 3.4 it will comile the templates on the first pageload. This is a very CPU intensive task which takes quite some time.
After installation I suggest that you manually compile the templates with the eztc.php compile script which comes with eZ publish.
You will find more information about the template compiler here: http://ez.no/ez_publish/documentation/development/scripting/supplied_scripts/template_compiler
Once the templates are compiled things will be much much faster.