Zach Holman on Photos.app
github.com
github.com
Yes, you could sync all the library to flickr, and it would work like a charm (btw they updated the mac uploader, worth a try), but you would still lose all the benefit of having them in your computer.
Now that's possible, and you can also have less disk space and "reclaim" the real photo whenever you need it.
That's a big improvement.