I have a Belkin matte screen protector on mine, and it definitely makes the Xoom far more usable in sunlight. They are like $20 at Target for a 3-pack - I highly recommend them, and here is a tip for installation.
Clean the screen thoroughly first (obviously), get rid of any streaks. Then using a spray bottle, mist a little bit of water (with nothing else) onto the screen, and then apply the protector. This will let you position it, as these protectors are completely 1:1 same exact size and dimensions as the Xoom's display. Then, use the card that comes with it to remove any bubbles and excess water (keep a paper towel nearby for when the water comes out of the sides, but you really don't have anything to worry about). You will see some excess moisture under the screen for a little while (depending how good you swipe it out), but I assure you after a day or two max, it will disappear completely. Hope this helps.