BuddyPress/MultiSite - Change to SSL & www as default?

I would be curious to get some feedback on a couple things I am considering. I have a BuddyPress/Multisite website hosted on wp-engine that goes live in next month, and I have done a fair amount of work and configuration. I have two changes I am considering. The first one, going to SSL, is one I probably will do, but I would be curious to get any feedback. Any gotchas with a change like this? Is it worth the time and ongoing expense? From an SEO persective it seems it might be, but would love some thoughts.

The bigger question is right now my site defaults to not using www as the root, and as I read about the process I am reminded of several much simpler site migrations than this that led to a lot of work getting everything back and running right. Is there any reason that I should move the root to the www subdomain? The only reason I was leaning towards it at first is just because google, facebook and so many other big sites tend to do that, but if there isn't really a benefit why bother.

Thanks! David