I know this is a subjective matter, but I prefer summary feeds or excerpts when scanning the latest posts - if I want to read the post, I'll click onto the site. Some feeds, however, show the complete posts, which can be long and take time to scroll by. This bugs me.
Can Google Reader be convinced somehow to always and only show post summaries or excerpts?
This is not exactly what you want, but I view my feeds using the List view in Google Reader. It usually gives me enough of a preview that I know if I want to open it or not. It helps me filter out the not-so-interesting feeds and focus on the one's that pique my interest.
It's not ideal, but what you're suggesting is that Google force a summary out of the feeds - which is not exactly up to them, in my opinion. That's just the way the particular web sites are posting their feeds.
Try the Better GReader Firefox extension. It can optimize a lot of the GReader features.
Many sites offer excerpt feeds, so check if the sites you are looking for offer a feed like that.
For example, Lifehacker does.
Otherwise - and this is just a guess - would Yahoo pipes allow you to limit the amount of characters that come through per post?
I think it is up to the website to put the first paragraph in bold. I.e. <p><strong> para text here </strong></p>.
