The whole "government is evil" and "fiat currencies are doomed to fail, hoard gold!" sentiments all over this forum are a real turn off. In America extreme-libertarian views seem to be in fashion, but for the rest of the world those sort of arguments just make you look paranoid and juvenile.
The way I would describe Bitcoin to people is sort of like a Paypal replacement, but one where your account cannot be frozen based on the whims of a computer algorithm, and 'undesirable' customers like Wikileaks cannot be dropped from the system by government pressure. Basically, a secure and fast way to send money between two endpoints on the internet, without needing to have it approved by a third-party. I love that the scarcity (and hence value) of the currency is derived from the laws of mathematics (cryptography in particular), but 99% of people have never heard of Public/Private key cryptography, we probably need a good metaphor to explain that part.
I would say the #1 priority is making Bitcoin easy to set-up and use by merchants, maybe a new YouTube video with that as its major theme. The #2 priority is to make it easy for people to transform dollars into Bitcoins, there needs to be a Dwolla-like method set up in every country in the world, at the moment only Americans can easily get a hold of Bitcoins without mining. The #3 priority is making the client more user-friendly for non-technical people, in particular backing up and securing the Wallet.dat file is essential.
Just my 2 cents.