The plugins available to a WordPress site are what can make it a really powerful tool, with some scripts providing the most obscure functionality but can give the blog that extra little zing.
Having said this, many plugin developers do not keep their plugins up to date as fast as hackers are at writing new methods for hacking the blog. Some WordPress updates offer changes that aren’t compatible with the plugin and if it is a core plugin script like something that promotes featured content, layout plugins, or worse yet, DB backup plugins, then updating the blog to the current version can render the site useless, or at the very least, ineffective. Both WordPress and Google (for some reason) mention a few times that blog owners should update their blogs as soon as possible, but how long do you wait for your plugins to be updated before potentially moving beyond their version compatibility?
There is a reasonable solution. Run a dummy blog site and use it as a test bed for plugins and updates, and simply beat the hell out of it. Another benefit this brings is that the dummy blog can also be a theme repository, housing all the themes you’ve run across so that you can review them at a later date.
Building a new project with a new style will be a lot easier when you have a style to use for modeling, right off the bat.