The Gold card does have a lot more benefits than just the 10% off. (Although, as noted above, you can get free wireless with ANY Sbux card, and the Gold card does NOT get free coffee refills!)
I signed up this year for the heck of it. Besides the free drink for signing up and a coupon for another on my birthday, I have received several other offers/benefits: A few 10% coupons for friends; The free Vivanno smoothie, and 2 50%-off coupons (wasn't that great--I make better ones at home!); a free pint of Sbux ice cream. Those right there add up to around $15.
But the best perk was an invite to an event 2 blocks from my home for the debut of the Sbux Via instant coffee back in February. This was a relaxing event in a nearby loft space, with a 5-minute talk by the Sbux CEO and an open bar for about 4 hours, along with Via coffee to mix and sample, and lots of hors d'oeuvres being passed around. The drinks alone paid for my Gold card. Plus there was a goodie bag with an African cloth bag and one of the Via travel mugs that holds 6 Via packets. And I left with about 20 more 3-packs of Via (they encouraged us to take as many as we could carry!). That is probably worth another 2 years of Gold card fees.