Do you have any examples or references of "story" that I can learn from?
PS: Yes, I know about exclusives. Therefore, I didn't do a mass-mail. I mailed one, waited, mailed another, waited. But still no reply.
Maybe by changing your subject line to fit their typical "story" type. Like using LifeHacker as an example: "How my software improves conversions by 35% - overnight." - just something a tad bit sensational.
Also, you might want to consider doing "favors" for the bloggers, like giving them a free account & personal assistance in setting up some a/b tests for things like their events or contests, etc.
Also, you can try to reach them more personally (but they usually don't like that) - if you have a particular persons email, give that a try or twitter if they're following you, dm them or even a call, if you have skype credit. I believe Jason Kincaid from techcrunch is jkincaid here on HN, that's a starting point.
Lastly, you might want to approach blogs with smaller audiences, that are targeted, like smashingmagazine.com or appvita.com - something that 90% tech people read.
Good luck, I hope this was helpful.
You have plenty of data to play with and I'm sure there are extremely interesting points you can make.
You need to focus. The e-mail you posted here is well written, but too generic to make an impact nowadays. You need to tailor your story to fit the sources you're most interested in. You will not get coverage on even three of the sites you mention, since they're all keen to get exclusives, so don't bother with the mass mails. Foster some relationships.
Look at the blogs you're targeting. Really look. Your e-mail provides no story - it asks me to come up with one and try to fit you in to it. This distinction is important, especially for Mashable, RWW, and LifeHacker. Go through their stories and look for patterns. On RWW you'll see a mix of "news" about well established companies and "how to" type stuff often featuring smaller companies (like yours). Mashable is very list and "soft" news oriented (note posts about Justin Bieber, dating, and "happiness." LifeHacker is very "how to" based.
Your story is basically "news" but it's not a "story." You need to seed the bloggers who are looking for stories (like the above three) with stories, not release news.
(I could write a lot about this but I've been up ages and need to get a few hours sleep before going to the in-laws.. I hope you can sympathize.. :-) Any questions, ask away and I'll be back later.)