I've written about my unhappiness with partial entry syndication feeds before. Another limitation of partial feeds that only struck me recently is that you may well get no sign that an entry has been updated after you've read it.

With a decent feed reader, any change to the text of an entry in the feed that you've already read gets flagged. With full entries in the feed, this means that updates get flagged. However, with a partial entry the update may well be made to stuff that is after the partial entry cutoff point; it seems to be common to put the 'updated:' notes down at the end of entries, for example.

(Admittedly this only applies to updates to entries that are recent enough to still be in the syndication feed.)

A good partial feed system would put in some explicit 'updated on' marker at the end of entries when the entry was modified after its initial publication. However, this would take extra work on the part of the software and I don't think I've seen a package that bothered.

(In theory you could just update the entry's Atom 'last updated' element or the RSS equivalent. In practice, I don't believe that very many syndication feed readers will flag this as an actual change, and many of them don't make this date very visible to the user anyways. Changing the text makes it more likely that the user will be able to figure out why an entry is flagged.)