Did you allow them to use your bathroom and offer drinks and/or snacks? Dh owns a contracting business, you would be surprised how awful people can be.
If you want to, they would appreciate a tip, but you aren't required to.
The super nice people offer snacks -- a bag of chips/pretzels goes a long way to making an install guy happy. On a long job, dh and his crew are frequently offered lunch. They decline, but some people just order hoagies or pizzas for everyone. Guess which customer gets a little extra work done for free?
Dh was working on a clients house and they own a restaurant. They sent him a gift card and a nice thank you once the job was finished. When they called for a second job, dh gave them a sweet price because they were really nice people.