OK, here's the deal. I've implemented image gallery nodes in D7 the straight-forward way, i.e. create node type 'gallery' and add an imagefield with unbounded number of values. Nice markup via Views/EVA, done.
Now, to make the image upload convenient, I tried the following ways and got the respective results:
Multiupload Filefield Widget: The uplaod goes through, images appear on server side, but php runs out of memory while computing the ajax response for the upload.
Plupload widget: Upload works, but side crashes on save. I get lot's of visible json instead of the saved side.
Plupload via Fielfield Resources: Upload goes through, after that no visible response. On save, I get a long list of copy/rename error messages above the actual side.
The problems are present for pure file fields, on a otherwise pure D7 installation, so image processing is off the table as well as memory polluting modules (up to the ones mentioned above, appearently).
So the question is, why is it so memory consuming to compute a not so lengthy ajax response? The side shall collect several galleries containing each around 200-400 pics, so a nice way to bulk upload those jpgs would be great.