Tcpreplay 3.0 was released as its 10th beta this week. It's actually a suite of tools now (I haven't used it in a very long time) including: tcpprep, tcprewrite, tcpreplay, tcpbridge and flowreplay. Read about them here. Hint: scroll down to the bottom to find them, the wiki also talks about Trac, which takes up a lot more space in the wiki.
In any case, this is one of those tools that you need to know how to use if you're going to analyze traffic (though I seem to remember it not handling broken packets well).