The fairly recent improvements in digital photography have greatly enhanced survey reports - it's a cinch now for the surveyor to include detailed pics of the various things (good and bad) that were found.
In addition to a seperate engine/mechanical survey, having the rig inspected by a qualified rigger will add to your peace of mind, while lightening your pocketbook just a little more.
I agree with the idea of being present during the survey - can't really see how a confident and capable surveyor can object to that, and you do get first hand impressions and immediate feedback as well as the opportunity to learn from an expert.
In some cases, it may be possible to have the surveyor agree in advance to abort the survey if you come across something early on that is a deal-breaker. That could save you some money there however some surveyors may take the view that they booked the time slot for you - end of story.
On the other side of things, some boats are so inherently simple that the insurance company's insistence of periodic surveys doesn't make a lot of sense. We had a M242 - all glass dayracer, not a single thru hull, no fixtures, no machinery - the simplest boat in the world and had to have surveys done 3 times over the 15 yrs we owned her. The first pre-purchase one was a no brainer, but the others seemed a nuisance and unwarranted expense.