I inspected a house built in 1948 the other day which had some upgraded systems.  Unfortunately it was a shoddy job.

Though they had just upgraded the electrical system, they didn't bother to do anything about the corrosion at the right service entrance cable.

They upgraded the electrical system but for some reason decided to install a sub panel instead of installing a new main electrical panel.  Nothing wrong with that in and of itself but there would be less equipment with just a main electrical panel.  However, there was a problem that the sub panel was built in a plywood box that was not properly weatherproof.

The sub panel is only a few feet from the main panel, yet they didn't spend the money to run a solid cable to the sub panel.  So they have an open splice in the sub panel area... and worse of all, they spliced to different sized wires in which one is now undersized for the 100-amp service, a serious hazard. 

At the sub panel they decided to double tap instead of just adding another breaker.  There was no need for this.

There was undersized wiring for the 30-amp breaker, once again an immediate hazard.

They also left an old-style screw breaker with frayed wires and open grommet holes, instead of just upgraded it to a breaker.

The furnace and A/C unit on the roof had also been upgraded, but not the ducting system.  They used the wrong type of material for exterior ducting and it was torn, so air was escaping to the exterior.

The duct was also losing air into the attic and therefore needs to be sealed properly.

Some of the plumbing pipes had been upgraded, but there was a leak.

Also, water runs downhill, so there's no way that this 4-way connector can be effective for drains at all 4 sides.  Water cannot be flowing downhill from 4 different sides, a basic law of gravity.

Luckily the agent had convinced the buyer to do a home inspection as he was hesitant because he did not believe it was necessary since the heating/cooling, plumbing and electrical had been upgraded.

I hope this gives you a little more information about a home and the value of a home inspection.