I've yet to take the plunge myself with running a kickstarter campaign, but having backed a number of projects that have subsequently been cancelled, I can't help but feel let down by project creators.
There are some advantages to letting a kickstarter campaign run its course to the end of the period. There may be a magazine article that highlights the game and leads to a spike in contributions in the dying days, or equally it may be a few retweets by people with lots of followers leads to a renewed flurry of interest in the campaign beyond the immediate circles of people the game developers and their friends hang out in.
People who have already contributed and want the campaign to succeed may decide they will increase their contribution after all to try and tip funding over the edge, or equally make a renewed effort to rally their friends and contacts, who may not have heard about it the first time round, to pitch in.
Kickstarter has evolved from something semi-altruistic into a pre-orders and marketing platform, and cancelling a campaign early, especially if you have plans to continue development by other means, will inevitably mean lost sales
However, the biggest impact is the message it sends to supporters about the project creator. Rather than share in defeat and disappointment with their backers, and move everyone together to the next stage, the project creator has instead taken the decision away from the supporters and back into their own hands. "I'm going to let the crowd decide if this project should succeed. Oh wait, actually I'm going to decide myself after all, and that decision is the opposite of that made by those who supported me"
I've never left a football match early, even when my team are losing. I'd rather stay till the end, because once in every while, there will be a late comeback, and that magical moment when it happens is worth a thousand disappointing realities.