What are those 'DLC' games like?
I've only ever stuck with 'Puzzle Swap' and 'Streetpass Quest'. Do other people need to own the DLC things to use them? Are they actually fun? Are they worth the money?
It's hard to judge these things for myself with the little amount of detail Nintendo gives about the Streetpass DLC.
StreetPass Squad is a space shooter of sorts. The people you get by StreetPassing become attack pods, the color they are determines what kind of attack they do (red is flamethrower, white gives you sawblades). It's pretty challenging, at least for me it is. There's a bunch of extra things to complete, like collecting all gems, not losing any attack pods, etc.
StreetPass Garden is just a flower breeding sim. People you StreetPass come over and water your plant, if you both have a plant that bloomed then it can cross-breed and give you new breeds. There's also customization for your garden, the pots plants are in, and you can do jobs where you need to grow specific flowers. It's relaxing, but once you get to the last few (I've grown 76 out of 80 so far), it gets really hard to obtain the last ones you need.
StreetPass Battle has you conquer the world by building an army. People you StreetPass are used by having the number of people they have in their plaza added to your army. If they own the game, then they will challenge you to a battle instead. The battling itself is just a game of rock-paper-scissors.
StreetPass Mansion is a semi-horror RPG of sorts. You get into encounters with ghosts, you get weapons that you can level and upgrade, it all works on an HP system. In the mansion you go through floors and try to find the stairs so you can get to the next floor. StreetPassed people gives you tiles to use. The more you SP one person, the more kinds of tiles they're able to give you. It also has Ella Mentree who should be the new 3DS girl.
As for if it's worth the money, if the price was lowered everywhere I'd say it is. I bought it when the pack itself was still €15, it's now been lowered to €10. Apart from Squad I play them every time I get tags. Squad is just a bit too much trouble for me, and I feel like I almost have to use a guide for it. Or I just suck at space shooters. All in all though, I don't regret my purchase. They're quirky and have a lot of content.