As a candidate, I'm the most excited when there are short contract/work sample coding challenges that are problems directly related to the job I'm applying for, and I wish more companies did them than whiteboard stuff. It tells both parties the most information out of all of those options. To the employer: "Can this person do the job, or not?" Pretty simple. To the candidate, I think a coding challenge can tell you a lot about the company and what type of work you're going to be expected to do. I think it weeds people out much more effectively than whiteboarding. Making time for this part of thing is part of the job search, the same as scheduling an onsite.