With all the talk about the new SX60 this topic had fallen off the page but I have an observation that will also likely apply to the SX60 as well.
On the build-in digital 1.5 and 2x teleconverter, there is a second use for it that I've been using increasingly.
On dark and gloomy days when the SX50 just doesn't have the light sensitivity that I think that a lot of us wish it had, I find that using the 2x converter allows me to back off on the optical zoom and allow more light in for a given object that I wish to frame.
That happened this morning. Very dark, gloomy day. There was a deer in the yard and using only optical zoom the SX50 just couldn't get the light needed to focus. So I backed off on optical zoom and flicked on the 2x teleconverter and it was finally able to get a decent focus.
The deer photo is a focal length 75.98mm, F/5.8 and shutter speed 1/25 sec.
It was in the center of the second photo but left.