Theme Switcher Reloaded plugin by Themebot allows the viewer to make a selection from available themes and it does it well. This plugin is being used on our website ( see the sidebar ).
It is not uncommon that our websites become slow. We have to remember that majority of viewers are not very patient and will not wait until our pages load. There are countless reasons for website to become sluggish. The following article - Better permalink rewrite code by Milan Petrovic deals with one of them.