The biggest problem I find once a script or program is complete is making sure it is working as optimally as possible. Usually a second set of eyes is needed to check out the overall performance of the code.
The hardest thing is finding a person with critically significant level of expertise and experience. They need to be able to stop redundancies that occur with unnecessary processes. Depending on the execution load and the resources each program takes up, an additional extra loop here and there can multiply the time it takes to execute a program. In today’s fast pace world, a millisecond is forever long time.
The next evaluation of the code should optimally be by a security expert. Preferably a hacker/cracker that thinks of ways to go around the known security features currently installed. Unfortunately every level of security taxes the resources that the program uses, and therefore slows down the execution level of any program.
You need additional eyes that can balance out the speed versus security problems that occur to create a bulletproof, stable, and sound program. This is why the open source community is so successful. There are literally hundreds of coders that critique code and exploit vulnerabilities in programs to benefit end users.
A great example is when security vulnerability is found in a Linux program, usually within 2 to 4 hours a security patch is created. This is done with collaboration of hundreds of coders. If a security vulnerability is found in a “Microsoft” program, it can take 2 to 4 weeks before a patch is found. 2 to 4 weeks is forever and can seriously imperil the integrity of the project.