If a joint in the plasterboard is bad to start with, a thin skim of multi finish will NOT make it look good, it'll always show through. I'm a great believer in using bonding coat first, then multi finish. Another thing Chris,did the plasterboard have "tapered" edges or square edges.It looks to me as though they were "square edges", which makes an uneven joint look more obvious after skimming. As I said earlier, Bonding coat first, gives you a chance to come and go with a bad joint, it can be feathered/blended to look far less obvious. Each to their own maybe, but it's the finished look that counts.