The ease of use, it's flexibility in working with different types of projects (residential/commercial).
Also is great for creating wiring diagrams which are used by many inspectors during inspections to ensure that the electrical work complies with local codes / regulations etc. Nothing really - but I do wish there was an option so we could see what each wire would look like before applying colour or marking out where wires were run through walls; this helps keep track when putting up drywall. This has helped us create more accurate drawings than using pen & paper methods alone!