not sure why there is so much resistance here about doing an 8 hour test, I might be in the minority but for a traditional whiteboard interview I would spend a lot more than 8 hours revising algorithms and so on, and have a lot of stress due to whiteboard coding not being anything like real coding.

Being able to take a Sunday to work on a challenging problem in my own editor / computer / dev environment sounds great! I wish that all companies added in their job ads something like 'if you want to skip the whiteboard send us your solution to this problem together with your resume' where the problem is a representative problem of the type of work they do, then you spend the interview discussing your solution as opposed to playing algorithm-roulette.

It would also cut down the uncertainty when you see a job ad where they ask for all sorts of different languages / skills, if you have fun doing the coding test, it's likely you'll enjoy working there, and vice-versa (in which case you might decide not to even apply)