How do you combine exposed filter string text searches into one input field for Drupal 7 Views?
If you want to be super-flexible in your search, essentially searching through the whole listing rather than just a particular field or two, I'd suggest you simply add the 'Search Terms' filter.

If you go to add another filter to your view, you can narrow the options by the 'Search' related ones and select the 'Search Terms' one:


You can name it anything you want, but it will essentially search through your entries the way a regular search does - so, by default, it will search through all fields that are displayed on your node, not just the ones you're displaying in your view at the moment.  Hope that makes sense - just another option to consider in the mix.  :-)