Hola Munchkins!
Now, I am serious about my skincare, I have a veritable cornucopia of skincare essentials, non-essentials, add-ons, emergency stash etc etc, but toner has been one part of my skincare routine that I always felt was OK to skip.  Lately, I've decided to up my toning game, and use a toner every day, morning and night.  
Currently my toning stash stands at the Clarins Toning Lotion with Iris - aimed at my oily skin, plus of course, although not a toner, I also am an avid Liquid Gold user.
So, with my experiment nearing the month mark, what have I found?  Well, once toned, my skin seems to be more receptive to accepting the various potions I then put on it.  My skin is also evening out in skin tone quite well - now this could be to a number of factors, I have upped the ante on my skincare in general, and stopped flitting around like I often do with potions, but there is no doubting that my skin now needs less foundation.  So, in conclusion, toning experiment seems to yield results!  Perhaps the results aren't exactly pin-pointable, but toning definitely benefits my skin.
What are your toner views and recommendations?
Love A.x