After using it for past 6 months or so now id go with mixed medium dual trim not the sill. Its a good brush dont get me wrong, i just dont think its up to every day in and out, picking up new jobs etc, maintenance cleans are fine but new cleans are a bit of a nightmare, the sill brush collects all the crap in the brush then i end up spreading it over next window.
Ive just bought a dual trim, much happier with it, its that little bit 'arder
Sill brush is good tho
just not 'ard enough for me