I do like the interface, but in Firefox it's quit unresponsive and clunky, but a lot smoother in Safari. Either way, it was still quite difficult to actually find the start and end points I wanted. Not sure if this is something YouTube's end, like not allowing access to that certain point in the video.

I agree with other(s) when I say the quality is quite terrible, but hopefully some tweaks with FFMPEG, or maybe even another route.

I do like the neatness and unobtrusive-ness of the watermark though.

I think over all, it shows a lot of promise, but need to fine tune those UI controls and make it clearer/easier to select a timeframe, and improve the quality of the GIF somewhat too :)