I have been a Flickr user for a long time already and I have gigabytes of images hosted there, some of which I have uploaded directly from my mobile phone (no local copies). I have thought of downloading the photos using third-party tools but I have not found one that can reliably do it.
Uploaders, on the other hand, are plenty – ranging from stand-alone Flickr provided tools to applications plug-ins or even to built-in features in applications. So no problem in uploading images.
One tool was recently brought to my attention that allows me to do both reliably (of course, it depends on how reliable your net connection is). FlickrFS is a user-space file-system hack that allows you to mount your Flickr database as a partition and move, copy and delete images/files at will. Sounds cool, eh? Will try it and see if it is any stable – why don't we try it together?