a) No. I don't think it's too simple. I mean, look at Twitter? :)

b) I imagine people may want to personalize it, but I don't think that is something you need to worry about just yet. Keep it lean and mean. But that's my personal opinion.

c) Get them to flag individual items in the mail they get (I want more of this, I want less of this)

One thing I missed when going to the site was the ability to see what the last 2-3 days mails looked like. Before I sign up I'd like to see what I'm getting in to. :)