Congratulations! I'm now a lowly Gold, but was a 1K for a number of years. Here is what I liked about that status:

• Pre-boarding: nice to not have to join the massive group 1 line when boarding - just linger in the gate area and board after those needing extra assistance and Global Services. In most cases you will be one of the first on the plane
• Free food and drink in economy: if you are flying in coach and the flight is long enough to have the "bistro on board" you can get a free snack box or hot food item and a free alcoholic drink.
• upgrade priority: even as 1K, upgrades on domestic flights are not something one can count on any longer, but at least they did happen occasionally when I was a 1K.
• Plus Points: On most international flights I flew in Polaris using plus points. It was bizarre to be back in coach on long-haul flights once I lost my status! You can vastly increase your odds of getting upgraded if you purchase a Premium Plus seat and then apply points for the upgrade to Polaris. If you are fortunate enough to fly in paid business class, you can earn lots of goodwill with family and friends by sponsoring their upgrades using your Plus Points!!
• Customer service: while the dedicated 1K agents are a thing of the past as far as I know, I still generally had good experiences with customer service on the rare occasions I had to call in.
• Star Gold: since you are moving up from being silver, having Star Gold status means a lot when traveling internationally - lounge access even if you're in coach and a generous checked baggage allowance.
• Don't expect any special treatment on board your flight, but it did happen once in a while that a flight attendant would approach me and thank me for being 1K.