Bob Mixon posted about thoughts on changing how feeds are delivered for his site, one being full post text vs. truncated text that only shows the first few lines... I posted a comment but this is one of my pet peeves so I have to say something....
I HATE when feeds come in truncated. I totally get the thought process from the bloggers side, hey I want people to come to my site and see my stuff (and click on my AdSense) so I will make it a teaser and they will click through to my blog for the rest! WRONG. I bet 9 times out of 10 the reader passes on by because they don't want to take the time to visit your site.
Think about it, most people have many, many feeds, and we are all busy. We scan our feeds via some (crappy) aggregator, mark what we want to check out or read what we want and move on. Adding site visits to the process slows it down considerably and I for one am much more likely to just blow off a post that requires me to visit a site.
As many things in life, it all comes back around to usability. A blog is there for people to read it, don't stand in the way of how people are most likely to read it... in the comfort of their own (crappy) aggregator.
P.S. RSS aggregators suck... is it that hard to build an awesome one??