I'm must be one of the worse swappers about the 6/6 Plus and 6S/6S Plus! I've had a 6 then a 6 Plus back to a 6 to 6S and now a 6S Plus since October 2014... 5 times!
I've had the 6S since launch and just craved for the larger screen, battery and the OIS. Just got a 6S Plus yesterday (Lucky, as they're being snapped up in Hong Kong). Yeah, the size is a tad awkward but I think I've overcomed that finally! Returning the 6S and Apple was really awesome waiving the restocking fee for me too!
I did something similar. I first ordered a 6+ but my initial reaction was, "its too big" so I exchanged it for a 6. Then I played with someone else's plus and decided I wanted that one, so I got the plus. Had it for a year, complained about it, then upgraded to a 6s found myself missing the plus so I ordered a 6s+.