For this particular game, DLC seems to be the only way to include characters that couldn't be secured for launch. It's already been established that some publishers weren't eager to hop on board day one, so no Cloud, Crash, Spyro, Sora, Snake, and other character's who's names start with the letters "C" and "S", on day one.
I think most people, when seeing, say, Cloud, as a DLC character, whether paid or free, won't care that he wasn't on the disc. He's a highly sought after character, many fans of this game will want him.
As for learning how to fight against a DLC character, there have been a few MP games I've played where, even if you didn't own the Map, you could still play on it, you just couldn't host/create a match with that map.
I imagine that, if, for example, I have purchased Cloud, but you haven't, I'd still be able to fight you as Cloud, but you wouldn't be able to fight as him unless you got the DLC.
I'm not as hung up on DLC this generation as many others are, but then again, I don't plan on playing this game online as much as I know many of you are. I'll probably spend most of my time in single player, or playing couch matches with my friends. No offense to you NeoGaffers, but I don't have much desire to play you all in MP in this game. Nothing personal, I'm just a single player gamer first and foremost, and an MP gamer very, very low on that list. I probably do 95% of my gaming solo, with 5% online, and sporadically.
I enjoyed playing the beta with you guys, for sure, but I'd much rather play against people actually in my house. That was one of the things I loved about Smash the most.