I have a large board that doesn't use SSL. I'm looking for info as far as using an SSL as it relates to Xenforo. What are the negatives to installing it? To those of you who have, did you notices any changes?
Will it affect my current indexed pages? Site speed? What positive benefits am I likely to see?
Any way to deal with http links and images that already exist throughout the board?
As brogan said a quick query to find and replace existing links works. But you are going to be using a redirect to force https anyways. There are a couple of plugins that upload images hosted elsewhere automatically. The upside is no warnings about mixed content from non SSL sources but the downside is attachments taking up space. I think there was some sort of image proxy system to take care of this now? I haven't looked into it.
It can help Google rankings. Its good for customer image. In the end the client and the server are still points of vulnerability. In my opinion its good for image, but a false sense of security as well. Apparently the initial connection negotiation takes longer, can be dependent on hardware. I have my SSL site on a well tuned VPS and since its faster than my other sites I can't say I notice anything.