This is an issue that keeps coming up- and the way to judge is: is it something every visitor coming to my site might want to read? Good “Page” content would be: a contact page, a bio or about me page, legal information about your site, a reference page, or my favorite- a list of all your competitors- so you can not only make a statement: “here is my competition- check them out”- but to also have a shot at being part of the “evoked set” when someone is searching for your competition. Here is an example in my site “Agencies that aren’t The Next Wave” which brings a lot of hits – from people who are probably in the market for services similar to what I offer.
For the more advanced websites- a page can also contain code that may not use the style sheet of the “post” entry- so that you can have a different layout. The next version of Word Press (1.6) is rumored to have more flexibility in this area.
Some themes don’t make automatic page lists- and only offer a few static page buttons. These static buttons have to be hand coded to link to the Pages you create in Word Press. The CoffeeCup theme is one example- as used in this site: www.davidcousino.com