I've finally begun the transition to Flickr. Though I've had a free account for quite a while, I've been hesitant to move to a Pro account; something I've written about before. What pushed me over the edge was the free Pro account (for a year) I received from Richard (old Pro users were given some invites; a side effect of the Yahoo! acquisition).
As I mention here, I plan to use Flickr as my primary photo-storage medium (and my home machines as backup).
I've already moved all of my "public" pictures to Flickr (i.e., the picture sets that used to be on my photos page) and have described/titled/tagged all of them where applicable (see the sets on Flickr). The Flick Export Plugin for iPhoto is brilliant and was absolutely essential in moving these sets over.
I think I'm going to hold off for a while on putting all of my other pictures on Flickr. As it currently stands, there doesn't seem to be a way to create "private" sets. All of my pictures are organized by event and/or month and I'd like to create sets that follow this convention but are only accessible to me.
If you create a set of "private" pictures (i.e., NO public pictures), the set will not be seen at all by the public. This, however, does not solve the case when picture sets that I upload and want to keep private contain pictures that are in public sets (for instance, the Personal Favorites set) — privacy settings are based on the picture, not the set, so if a picture spans multiple sets, the last privacy setting for that picture will be applied to every occurence of it (regardless of set), which will obviously make some of those sets that I wish to remain private, public. Yes, the pictures that I want to remain private, will stay private, but the set itself will be publicly viewable (and will cloud the "public" sets I want people to see).