Any SEO gurus want to give a brief low down on the value of SEF Patch (I've just bought the extended SEF Patch, so I'd like to maximise my ROI)
Then these are no gurus ;-) Seriously I'm in the SEO business for almost 7 years now. I always use META fields..
The patch enables you to apply good titles and good META data. Indeed some are saying that META tags are not that important any more. But do you want to bet on it? Applying keywords can not harm and for example is some cases google is still using the META tag description to display a summary of your site. Beside this the Title tag is the most important one there is and should be controlled fully (which is not the case default in Joomla). Also you want to prevent that some pages are included within the Google index (if they can harm your PR), therefor you can use the robot meta tag.... So who are these gurus....
In most of my SEO jobs I take no risk and apply always META fields as said before they cann't harm and will only increase the keyword density about your page topic.
And yes opensef and the sef patch works together: opensef is url rewritting and the sefpatch is all about META data (control) and titles.