This effect is one of my favorites. There's lots of other useful editing suites that produce a great job, I just listed a couple of the better known products. Ask your videographer which mixer they use, and get them to show you some effects. They all love to show off their computer setups, because seeing the setup leaves a lasting impression on the client, it totally wows you to see all the technology in action. Ask to see many examples to give you ideas.
Some effects can really make the video come alive with a party atmosphere.
If they refuse or give verbal claims, get up and leave. A written contract will help them remember. Just surf the alt.wedding newsgroup and see how many people got burned when they were not given what they expected and had no contract to enforce it. On the contract, you want it clearly stated who your videographer will be. Try choosing the business owner, even if they cost more, they have more experience.