Unlocking achievements and gaining Gamerscore may be an addictive if ultimately pointless diversion for many players, but dedicated achievement hunters will now get some tangible benefits in the form of an ongoing Microsoft Points rebate and special gift. A very small rebate, mind you, but it's something at least.
Your accumulated Gamerscore will unlock some tiered benefits so long as you've signed up for the Xbox Live Rewards scheme (you can do so now). If you've acquired 3000-9999 G, you'll receive a "special gift" on your birthday, which has a cash equivalent value of approximately 15p. Gosh, with this gift you spoil us, ambassador.
More excitingly, however, profiles with 10000-24999 Gamerscore will receive a 1% rebate on all purchases going forward - which goes up to 2% if you've accrued 25000 G or more. This will effectively net you between 8-16 Microsoft Points per 800 Microsoft Point Xbox Live Arcade game, which won't go very far but will add up if you're a regular user. Essentially you'll be able to afford a free indie game every once in a while.
Note that Xbox Live memberships and Microsoft Point top-ups are exempt from the promotion.
"You've been faithfully building your Gamerscore for years now," reads the accompanying blurb. "To reward you for your dedication, we've created MyAchievements for Xbox LIVE Rewards Gold members. The MyAchievements level that you earn – CONTENDER, CHAMPION OR LEGEND – depends on your Gamerscore. The higher your score, the bigger the reward!"
You can read more on the Xbox Live Rewards site.