This plugin generates an XML for every post using WordPress' gallery data system so you can use the generated XML with the Simpleviewer Flash gal
1) There's no way to exclude a photo from a gallery if it's one of the post's attachments. That's outside the scope of this plugin, as I'm working within the confines of the WordPress gallery feature.
2) It does not currently differentiate between photos and other types of post attachments, so it will attempt to treat documents, videos and images the same. I'll get that fixed in the near future.
3) This generates XML on the fly every time someone visits a single post. If you’ve got a lot of images and a lot of traffic, there could be a site performance issue. If anyone experiences this, let me know.