For starters the padlock is something they've added manually. Open up your bank and that, and see the difference. That was a bit odd for starters.
The Siri servers themselves are https, but the payment side isn't. Not sure why you think im 'scaremongering' people, this is a forum, to post issues, ask for advice etc.
After an hour, my card(s) did work, after receiving an email from them they temporarily stopped payments and that was the error message. Not exactly my fault, and for anyone with sense it would 'red flag'.
Get off your high horse.
In other news, it works very well.
I had to use the second server as the first was under high load, and I believe they're adding more soon (as per their twitter account). There's a slight noticeable difference between the 4S' and 4 Siri-it runs slightly slower (not the data sending/fetching, the time between recognising and/or parsing speech, but it's much better than I expected. IMHO worth getting if you want to try Siri, just make a note of their T&C's (basically no refunds, can shutdown at anytime etc etc, what you'd expect).