I've never had Davis before but I have had Nejat and Chettle. Nejat is an effective prof however he will force ALL of his students to participate in classroom discussions. Normally he walks around the auditorium and points at you to state your opinion or to give an answer. His intentions are good, and it's always okay to be wrong- but some people don't like to be on the edge of their seat waiting to answer questions as soon as the material is taught. I had him for physics 1B03 and 1BB3 in first year and earned a 12 in both so from my own experience I would say his course organization is excellent (he had detailed powerpoints closely derived from the text). There was an iClicker component to the course which he used to asses your participation. The final exam had a couple of questions exactly the same as the midterm. He even mentioned the hard ones from the midterm and reviewed them in class so we could do them successfully on the exam.
Chettle has a comparatively different teaching style than Nejat. He does not force classroom participation at all. He thoroughly teaches the material and infuses it with his life experiences etc., which I thought made the material very interesting. I can imagine some people may have found his lectures a bit boring. He made his own courseware notes (it was a ~150 page binder-book) and based our midterm/exam questions on the ones we did in the courseware. We had a textbook but it was for supplementary reading. There was no iClicker component in the courses I took, Medphys 4B03 and 4T03. I earned a 12 and 11 in these courses so again from personal experience I would say he is an effective prof.
Please reply back if you have any more specific questions about these 2 profs, I'd be happy to help.