While so much of the technical weblog universe is going through towels mopping up their drool over the rose-tinted "how many more thousand developers will it take to get a fourth project out of beta?" Google Software Development Process, Aaron Korver wrote an insightful piece a couple of weeks ago on the potential down sides of agile development.
If you think still think XP and agile means that some stinky fat man chained up behind you and get greasy potato chip crumbs all over your jumpsuit while leaping up gleefully to point out a missing semicolon once every twenty minutes or so, you really ought to read Korver's thoughts. Any measurable improvement in productivity will take work and application and dedication. A sober consideration of the potential benefits and drawbacks can only help.