I've noticed that the frequency that Google Reader updates a given RSS feed is based on how many subscribers follow that feed. Brad Linder of Liliputing was the first to point this out to me, and he's seen the same behavior.
What we think we've seen is that the more popular blogs tend to be updated within minutes of posting, and posts from the less popular blogs tend to show up late (and in clumps). The least popular blogs, ones with only a couple dozen followers in gReader, tend to show up as much as 8, 12, or even 24 hours behind.
I know for sure that this problem isn't related to FeedBurner; I've seen the behavior with the source feeds of my smaller blogs (Appazonia & The Unbound Book). Those feeds go direct from the blog to gReader and they are terribly slow to update.
I'm pointing out this problem because I've had a number of complaints about TDR posts being delayed. Sorry, but I can't do anything about gReader. But I can give you a workaround. If you want to get my posts faster in gReader then start a subscription to the following feed. You'll need to copy and paste it for this to work.
That is the URL for the original feed and it usually updates within minutes. But again, you will need to copy and paste that URL into FeedBurner for this to work. If you simply click on it you will be stuck with the FeedBurner feed.
P.S. That fix will help my readers with gReader, but it does nothing for the rest of the blogs I follow. I don't know about you, but I'm in the middle of a search for a gReader alternative. If you can find an app or service that can handle a thousand feeds, please let me know.