I have had several Hasidic employees, and they have been the most difficult to accommodate in my experience, primarily because their schedule of religious holidays makes it almost impossible to work a full year unless they are allowed to work from home. As a business operator, I was required to make reasonable accommodations. I was not required to let people work from home or work completely outside of normal business hours when supervision and interaction with other team members would be impossible. That is one of the reasons that you are likely to find most Hasidim working in businesses owned by other Hasidim. If you are shopping for camera equipment, you will learn quickly that B&H Photo simply closes down for major holidays such as Rosh Hashanah and Succos, which effectively makes them closed for half of September.
Atheists and Hindus have been the easiest to accommodate.
Religious issues are no harder to deal with than anything else. My approach was simple. I gave seven paid holidays as required by law, four personal days, 10-15 vacation days, and five sick days. If a person had specific personal or religious requirements, I was willing to work with them as long as the total time off taken did not exceed what our policy allowed and did not interfere with the business schedule. A few conflicts would arise over time, but religious needs were seldom the source.