"Though that applies to 'casual users' - presume anyone can pay the annual fee."
What annual fee? Currently you need to pre-register and pay £3 for a keyfob, which is sent out to you within a few days, many are arriving next day if registering early enough in the day. You can then pay the £1 daily access charge for each 24 hour period that you use the bike plus any usage fees that you make up.
If you're going to use the bike less than 45 times a year, it's going to be cheaper to purchase a daily membership.
Casual users (people who use their credit/debit card for identification) will only be able to use the scheme later in the year. They were meant to be able to from a month after the scheme started, however it turned out to be more popular than expected, and they need to increase capacity first, particularly at peak times at the London Terminals, where in the morning the racks are empty, and evening they are full.
On the hills in Edinburgh, I don't even think about cycling up the Mound, in that I just pedal up it, rather than avoid it! Hills aren't a problem once you get used to them. If you think Edinburgh is hilly, try the Isle of Man.
I was speaking to someone this afternoon, who has just started cycling to work on Monday, and has been saying that it's been a fantastic experience. He's getting to work in 35-40 minutes instead of just over an hour. It's the first time he had been cycling for over 15 years. I've been hearing a lot of similar things from various people in London.