The plugin (mambot) works fine, but seems to ignore links with a line break inside the anchor-tags.

Instead of adding an IMG tag to every external link, I would prefer the option to automatically assign a CSS class to external links. This would allow other decoration for external links, e.g. a different text colour, and images could be assigned this way as well. (I think it would be best to offer both options, the "hard" insertion of an image, and/or adding a CSS class.)

I had trouble creating Google Sitemaps with other solutions, but the XML output of SEF Service Map works fine.
So if you want to use this as a search engine sitemap only, just install the component and the included mambots (plugins), add mambots for 3rd party extensions (e.g. remository), publish the mambots, adjust SEF Service Map settings (in components menu) and finally submit http://YOURSITE/index2.php?option=com_sefservicemap&task=xmlmap&no_html=1 as sitemap address to the search engine.

I used this for two different Joomla driven sites. First was fine, but for the second one, Joomap did not include all articles and I couldn't find out why. As the latest news were missing, Joomap is inacceptable for this site. I had better results with SEF Service Maps.