I'm a Flickr "Pro" user (which no longer exists, thanks!) and here's what's bugging me about this:
Go here:
http://www.flickr.com/account/prefs/layout/
See what happened to the page where you could control the layout? All gone! You no longer have any say in how your photostream is displayed. I absolutely loathe the monster-pictures, black background and loss of data under each image. What can I do about it? Absolutely nothing! Some people may like the changes, or some of the changes, but it doesn't matter, you can either take it or leave, and if you read the official feedback page,
http://www.flickr.com/help/forum/en-us/72157633547442506/ it's about 1% take it to 99% "bite me."
With sites like this, you're either a customer or a commodity. Facebook, Google, Youtube: for all of those the customer is the advertiser and the users are commodities, and if you don't expect to be treated like a commodity, then you're fooling yourself. For a few, you can pay to get rid of the ads, which Flickr seems to want to move to. The problem is that for those of us who used to be pro users, we're now being treated like commodities, not customers.
I'll leave my account active, but I'll not pay them ever again, and if they offer the option of refunding the remaining year of my pro account, I'll take it. After that expires, it'll become an add-filled pile of garbage, just like everyone else's account. When flickr started, it was great, you were treated like a customer, and you had a great deal of control. Now, you're just image-fodder to get people to look at ads.
I have a friend who tried to convince me to move to smugmug. I think I will, until they get bought by Yahoo or Facebook and ruined as well.