You can only play 2 timecode decks in Traktor Scratch. If you upgrade (paid, of course, but I'm sure everyone's just going to download the cracked version) to Traktor DJ Studio 3.3 when it comes out later next month, you can play 4 decks, but still only 2 timecode decks at one time.not to mention the 4 table option in scratch.. and the latency issues as well.
And Serato still has a lower latency than Traktor Scratch.