I think the important thing is not to do a knee jerk reaction here, if you don't migrate to https correctly you will be in a world of pain!
Lets remember, right now it is a very weak signal and check your competition, are any of them https? probably not, so right now you're not losing anything.
Its the long term that worries me, it seems google is planning to strengthen this signal over time, the question is at what rate and ultimate how strong will it get ( my gut says it will never be a huge signal, but then every little helps).
In my view moving from http to https is the same as any migration ( to a different url or new platform with different url structure), if done correctly it should be painless but if done wrong can be disastrous. The other factor is if you have absolute links for elements pointing to http: they all need fixed, if you miss any then that page will flagged an insecure to the user.
Something I'm unsure about, I thought https is slower than http (and one of the main reason people don't https their whole site), maybe someone with more knowledge about https/ssl can correct me here.