My rule of thumb is, if something isn't working for readers, it's either because (a) the work sucks, which is probably the right answer but not the one I can do much about, or (b) the presentation is off. And I can do something about (b).
Sometimes the changes work, such as with The Harvest, originally published in paperback and given its title by the publisher in 2003. I never cared much for the title, which I thought was generic, so when I re-released it as an ebook, I called it Forever Never Ends, one of my original working titles for the manuscript, which was based on a song I'd written in a previous life. But the title and cover art veered from the book's real personality--which is a sci-fi/horror B-movie in text. When I finally went back to the publisher's title and gave it B-movie art, it found its audience (hit #1 in horror in the UK) and has gone on to fairly steady sales.
I changed covers for Disintegration, even though it was a Top 30 Kindle bestseller, and I even added a new ending (leaving the original as an alternate ending if people wanted to read it.) The new ending isn't a betrayal of the narrative, but rather a slightly less cynical view which better allows the readers to get what they want out of it. The book saved my sanity while I wrote it and was the bestseller that allowed me to make the move to full-time writing, so I am grateful. But I still changed the cover!
Changing titles is a last resort, something I only do if a project is headed for oblivion before its natural time. I don't know if Kiss Me or Die works (I used the art for a German short story, too), but with nothing to lose, I am spinning the roulette wheel. The digital age is ever moving, and ebooks are living things. And to those who liked an earlier cover better, all I can say is, "You had your chance to tell 10,000 friends to buy it!"
Of course, if this incarnation fails, this conversation never happened. If you don't love me, you die. Not much gray area there.
Free for Kindle, June 11-12 in Amazon US and Amazon UK.