That's been my big stumbling block--I realize the rules have changed for e-mail query (I still don't have a Kindle... ), but call it the "Elevator pitch", and I still can't imagine myself turning toward an editor I've never met, in an elevator at the SCBWI Conference, and suddenly starting the conversation with "Bill was having the worst week of his life..."
I'm with you - but as with an email query you have opened by sending the email in the first place, and the agent/ed has opened it, there would be nothing wrong with leading with - "Hi - I'm a writer... Can you give me 10 seconds to pitch you an idea?" as your initial contact!
Getting the basic idea across succinctly and with passion or voice is the imperative here. Although I don't have a wealth of publishing experience, I am fortunate to know a couple of people who work in the industry. They are receiving up to 30 queries a day, and from what I have gleaned from them, they CAN know two things within the first ten seconds of opening a QL email - whether they have read enough, or whether they need to read more.
The first option can be two ways - they know immediately that they want to get pages, OR they know straight away that it's not for them. Generally they read on after this point, but here's where human psychology comes in... They are loath to change their decision. Even in their own minds, they would be 'proving themselves wrong'. Even if the rest of the QL is great, they may well turn it down based on their initial impression, and likewise if it starts off well but ends a little weaker they may still request pages. They can decide immediately!
My point - simply put - is leave the ritual to the end. By opening your email, the agent is already welcoming the submission and expecting your pitch. Don't disappoint them. A courteous "Dear Mr/Ms..." at the start is great, but your title may well be in the email subject, and the rest can wait until the end. As long as your word count fits the genre, and you get the 'why I am submitting to you' bit at the right point, hopefully things will be dreamy ever after!
I can't speak for all agents - I have one agent who is a good friend (not in my genre, unfortunately!) and know an editor for a major YA publisher well, and another as a casual acquaintance. Not a huge number, but this is what I managed to glean from them under alcohol-fuelled questioning!