A warning: this full-day interview process won’t work for you if you don’t already know how to pair program. It can work really well if pairing is already part of the culture, but if not, it can go horribly awry.
What’s really nice about this is that the candidate gets a good feel for the culture – much better than asking “so, what’s your typical day look like” (and usually getting vague answers).
We are not thrilled with how much time it takes and would like to shorten it, but so far have no superior alternatives.
I know the prevailing interview process is 4-5 hours per candidate, but seriously, you and your team are going to be spending (hopefully) years with this person. Don’t apologize for how long it takes, ask why other companies don’t spend enough time.
This sounds really good overall, though I think the prospect of spending a day on site act as a bit of a filter. On the positive side is that the people you get in for that are likely to be highly motivated. On the negative, people who have problem taking a day off (and perhaps have too much integrity to throw a sick day) will be put off.