As long as he's used fibre tape on the joins then it should be fine, there shouldnt be any lines anywhere but occasionally you will see slight lines where the boards meet, especially if he's overboarded the ceiling, if these lines are everywhere then hes not done the job 100%, if he'd just skimmed over the original ceiling then thats a different story but he's skimmed over a plasterboarded one and the finish should be near perfect.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!