I like this plugin. It is quite handy. :)
I have a problem with adding new tags for the option 'Keep Markup'.
Once I added a tag, it shows up in the list of tags.
It seems to work - what means an <iframe> for instance remains in the excerpt.
If I safe the options the originally added tags will not remain in the list.
If I safe the options one more time. The originally added tags get stripped out of my excerpt again what means they don't stay in the options. So it gets automatically deleted from the tag list every time I safe the options.
It means I need to add all the extra tags again every time I safe the options page but as I already mentioned the tags do not show up in the list.