I've shot with pentax professionally for the last 18 months. I only shoot glamour/portrait. for studio work I never had issues with my k50. was waiting to see if the amount of work would justify more expensive bodies and lenses.
since getting that 3rd dial on my k1 I really miss it now on my k3 (which I picked up 2nd hand just before getting the k1). only ever set it to ISO or WIFI
but it's fantastic.
having shot with a canon 5dmk3 this last year... sometimes the AF is just amazingly quick but sometimes off. other times it's about the same as my k50. I'd rather stick with the pentax AF, plus for the shoots I do it's more than fine.
on a side note was chatting to a chap yesterday who used to work for "Top Gear" here in romania and now presents another car show and told me much he liked the photos I shot with a few models last week and the colour+skin tones. so much so that he asked me to shoot some models with a car they'll have next week, the day before they film their tv show...
so yep, pentax is better than great for professional work imho