Been using it for a bit now (Score 2)

The main difference about XP that I've seen is that you write test code (unit or not) before you write the code that it's testing. You do this iteratively, not in a big lump. XP has been working great for our team (hey, we're still on schedule).

As far as the "this will slow me down and I won't get to surf as much" argument: we have the advantage of actually having test code and constant code inspection, two things that I've seen many projects missing.