Posts out of order.
I thought this script was great when I saw it, but found out that it doesn't quite do what I would expect. When someone tweets, gets a reply, then tweets back, everything is out of order. The first tweet is at the bottom, then the reply is above it, then the first persons reply is above that...
When the conversation is longer than 3 tweets, it's even harder to follow. This is the same for either Firefox with Greasemonkey, or as a Chrome Extention.
At first I thought the same thing, but functionally it makes sense. It doesn't alter your timeline (ie it shows the Tweets as you would have seen them without the script). When there is a threaded conversation you just need to read it backwards.
The alternative is you seeing conversations started from people you don't know highlighted in your timeline. It must be in 'reverse order' to preserve the reverse chronological order that Twitter shows you. Otherwise the newest tweet may be a 10 day olds which happened to have a reply 5 minutes ago.