I use FP3 all the time with SPPS and I love it! You can modify pages very easily. If you've noticed, there's probably a small FP3 icon on your browser tool bar. Navigate to the page you want to edit and then click the Icon. Immediately after FP3 opens your page, copy all of the code to a new untitled FP3 HTML file and paste it. That way, if you blow up the page, you have the original code close by. (This has saved my a88 before!)
Sometimes FP3 will blow up the dynamically generated page title element. So if your page title is tweaked, look at the code very closely and you will see that a few <'s or >'s will have been replaced with "<" or ">"... That is really the only bug I have encountered. Hope this helps!
Robert Vignato