Pros

Thoroughly go through the aircraft, checking all parts and components. Worn or damaged areas that may have been previously overlooked, as well as poor workmanship, can be corrected.
Add Supplemental Type Certificates (STC’s) and enhancements.
Finnish the interior with the colors and styles of your choice.
Get a fresh engine overhaul to your own specification. Run the engine in and operate it like you want to.
New paint to your color and design specifications
Change the avionics and instrument panel to suit you.
Get a good working knowledge of your aircraft. Know where things are, how they work, how to fix them and keep them in good condition.
Increase you aircraft's value with low engine hours, new custom paint & interior, avionics and equipment.
Very satisfying work if you like hands-on experience.

Cons

It takes time and labor to complete a project. To some people, this is not a problem at all. However, it may be frustrating if you don't like to directly participate in the rebuild.
The project may run over budget if you find more damage and problem areas that need attention. Prevent this by doing your homework and research.
Damage history may affect the value of the aircraft. This depends on the type of damage and how it was repaired. In many cases, the value added by overhauling engines, updating avionics, and adding new paint and interior, enhance the value which may offset any damage history. Because of the age of the general aviation fleet, many aircraft have some damage history.