Both came from the same photographer who decided to sell his extensive Olympus Four Thirds system and move on to a Nikon D3 system. With my limited budget the best I could do was pick up the teleconverter and the flash (although I sure wish I could have picked up some of the SHG lenses he was selling).
My biggest reason for purchasing the EC-14 was to add a few more millimeters of focal length to the far end of my 50-200mm. With the EC-14 my 50-200mm becomes a 70-280mm f:4-5 telephoto zoom. In practice the E-3 detects the lens as a 70-283mm f:4-4.9. It's interesting how the measured values are slightly off on the far end of the range.
Olympus E-3 w/50-200mm + EC-14
1/320s. f/4.9, ISO 100, 258mm
In general use the E-3+50-200+EC-14 is no different in handling than the E-3+50-200mm. With the EC-14 I can now reach a little farther than before. That means I can fill the frame better at the same distances, or stand back a little farther than before (whether it's a 12 foot gator at one of the parks or a radar speedtrap).
The image above was taken wide open, hand-held, at base ISO. No special post processing, it was converted straight from the raw file. The focus was reasonably accurate and the shutter speed was right above the minimum recommended reciprocal for the focal length (258mm).
17mm missing front cosmetic piece
And finally, another shot of my slightly busted M.Zuiko 17mm, which I've given the nick-name Ol' Blue, for the bright blue plastic ring that is now fully exposed on the front of the lens. For both the EC-14 and this image I used remote control with the E-3. Both flashes were set up with one flash 45° to my left, with the second 180° on the right back side. For both images the front flash used the bounce card that comes with the FL-50R. For the EC-14 the rear flash was direct and 1/2 the output of the front flash. For the 17mm both flashes were set to the same power level and both were using the bounce card. The "background", if you want to call it that, was a single piece of 8x11" white printer paper.
There are times when I need to photograph small pieces of hardware, and the second flash will make it easier to do this. I had thought of purchasing a ring flash, but this has turned out to be cheaper and more flexible for other types of photography. And it's more fun to learn how to do lighting with two flash units as powerful as the FL-50Rs.
I wish I had the budget to invest multiple thousands of more dollars into another system (Canon 5D or Nikon D700, for example). But I don't so I can't. And the two items I just purchased used were cheap enough to fill in some capability gaps in the gear I currently have. And I might mention that even though both items were used, they were in immaculate condition. Their used prices were 40% less than brand new. And I can certainly live with that.