Just downloaded the latest nightly build (com_rsgallery2.2006-11-24.svn469.zip), uninstalled the "old" rsgallery2, and installed the nightly. But ftp-upload is still buggy... I have 25+ directories I need to upload, but no matter which one I try to upload, it says "No files found to process!". All dirs are full of jpg files, nothing else. And I've set them all to chmod 777 to be sure rights wasn't a problem!
I found the solution: The pictures has to be in the same folder as your joomla website, eg. if your website is in /html your pictures should be ind /html/uploads (or another subfolder) for RSgallery2 to find them. That solves the problem described above. I had all my pictures in a completly different folder, and that didn't work.
But now there's a new problem: All the pictures show up correctly as thumbnails in step 2, but when I press "upload", I get this:
- Error Image Upload : _lg_img_1558.jpg : not an image OR can't read JPATH_BASE/media/_lg_img_1558.jpg
- Error Image Upload : _lg_img_1764.jpg : not an image OR can't read JPATH_BASE/media/_lg_img_1764.jpg
- Error Image Upload : _lg_img_1775.jpg : not an image OR can't read JPATH_BASE/media/_lg_img_1775.jpg
- Error Image Upload : _lg_img_1776.jpg : not an image OR can't read JPATH_BASE/media/_lg_img_1776.jpg
- Error Image Upload : _lg_p1030001.jpg : not an image OR can't read JPATH_BASE/media/_lg_p1030001.jpg
- Error Image Upload : _lg_p1030002.jpg : not an image OR can't read JPATH_BASE/media/_lg_p1030002.jpg
- Error Image Upload : _lg_p1030003.jpg : not an image OR can't read JPATH_BASE/media/_lg_p1030003.jpg
- Error Image Upload : _lg_p1040019.jpg : not an image OR can't read JPATH_BASE/media/_lg_p1040019.jpg
- Error Image Upload : _lg_p1040021.jpg : not an image OR can't read JPATH_BASE/media/_lg_p1040021.jpg
- Error Image Upload : _lg_p1040022.jpg : not an image OR can't read JPATH_BASE/media/_lg_p1040022.jpg
- Error Image Upload : _lg_p1040023.jpg : not an image OR can't read JPATH_BASE/media/_lg_p1040023.jpg
- Error Image Upload : _lg_p1040024.jpg : not an image OR can't read JPATH_BASE/media/_lg_p1040024.jpg
- Error Image Upload : _lg_p1040025.jpg : not an image OR can't read JPATH_BASE/media/_lg_p1040025.jpg
- Error Image Upload : _lg_p1040028.jpg : not an image OR can't read JPATH_BASE/media/_lg_p1040028.jpg
...and so on for the 50 pictures I tried to upload.

Update: SVN 480 did the trick! Uploading as we speak

1621 pictures up so far.. This rocks!