The Quick Plaza runs a little faster (like the normal plaza does when you hold down the right trigger), but it's also been streamlined: Each Mii character only gives you their name and location, skipping details like their personal greeting and last game played. It's also a lot easier to boot up the StreetPass games, with their icons moved to the bottom screen instead of living in a separate menu as they do now.
The increased StreetPass limit definitely seems aimed at people who do most of their StreetPass action at large events. At conventions like San Diego Comic-Con or PAX West (happening this weekend) it's common for the in-game queue to fill up in minutes or even seconds due to the large number of players, instead of days (or even weeks) it would take in the rest of the US. It's included as part of StreetPass Premium, which means you'll have to pay for the service if you haven't done so already.
Nintendo also announced five new games for StreetPass, promising that they're all "bite size" so users don't have to worry about overstuffing their 3DS' storage. Slot Car Rivals, as the name says, lets players compete in a slot car race against the best times compiled from other players they've exchanged info with. Market Crashers is a stock market game where you predict stock prices based on advice from other Miis. Feed Me is a cooking game where you're tasked with preparing dishes fit for a king. The step counter in your 3DS gets a workout with Mii Trek, an exploration game. And Ninja Launcher involves launching half-naked Miis out of a cannon, just because.
Starting today, you can download any of the five games in the eShop for $3 each. As a special deal, you can grab either Slot Car Rivals or Market Crashers for free, and then snag the rest as part of a discounted bundle for $9.