On the subject of DLC, Skullgirls did it right: since the expansion pack re-release of the game was crowdfunded by fans, Lab Zero are releasing the new DLC characters as free downloads for the first month after their release, and paid beyond that. It's their way of thanking the fans for their commitment, but since they're an indie studio, they still need to make a profit and this is a good way of doing it without incensing the fanbase. You can also purchase new palette swaps for every character, individually per character or in an overall bundle, doubling the amount of 'swaps in the game.
Alternatively, Nippon Ichi also does DLC well: you've got the base game and the massive amount of post-game content, including new levels and characters, and you can purchase additional characters (usually the heroes of past games or newer titles, though they've also released such content as bonus mini-campaigns starring other characters, harder game modes, special pirate ships for the Item World and alternate wallpaper themes for the games' menus).
Basically, anything that's meant to be in the game is in the game, and there's a lot of content for what it is. Anything that's either brand new or couldn't fit into the base game, you can download at a reasonable price, but none of it is essential or necessary: it just embellishes the experience, and chances are you'll be buying most of it after you've already beaten the game and decide you want more stuff to play around with.
Skullgirls is even more applicable in this context: with the exception of Squigly (the first DLC character, intended to be in the base game but never made the cut), every character was voted into the game by fans. Lab Zero also decided to throw in two extra characters that weren't on the polls: Fukua, a joke character patched into the game as an April Fool's joke that became very popular and subsequently stuck around as a secret fighter, and Robo-Fortune, who will be the game's last DLC fighter. I think Smash DLC will follow a similar trend, with the most popular or potent characters selected from a shortlist and included in the game at a later date, and other top picks will be kept as high priority selections for the next game.
As for the poll itself, I have yet to vote.