Looking at usership statistics for RSS compiled by Syndic8, I think it's time to consider a somewhat controversial step: Deprecating the textinput and skipdays tags and perhaps other unused elements.
No problem with textinput - don't even know what it is about ;-)
But please don't deprecate skiphours. I added support for it int PyDS, so there actually are two aggregators and weblog tools supporting it. So it _is_ used. Damn, I hate removing code from programs, so removing the tag would really be embarassing for me ;-)
Skiphours is used by around five percent of RSS feeds, according to Syndic8. I wouldn't recommend it for deprecation. Skipdays, on the other hand, is much less popular.