I'm still convinced that he's the best option for the #4 spot in test matches, but as far as ODIs go, I think he should be getting the chop.
Many point to his experience, his good record and consistency. But the fact of the matter is, he ALWAYS bats in the top 4, and hasn't scored an ODI century since 2003. His supposed good record has seen his batting average now drop below 40 - below Hayden's whose ODI career was ended for never cementing his place as a permanent ODI player.
Since the Ashes, when he was dumped from the test side, he has often looked lazy in his dismissals - something you don't want from a specialist #4 batsman. He has averaged 25.29 in ODIs in this period..
Now this would all be understandable if he was an up-and-coming prospect with a future, but Damien Martyn hasn't done anything significant in ODIs for quite some time, and he is supposed to be the experienced, finished article used to patiently get Australia through tough periods.
People whinge about Katich at the top of the order, but Martyn has scored at a similar rate while batting #4 at a much worse average.
ODI batting averages since the end of the Ashes:Code:Mike Hussey 73.16 Andrew Symonds 48.44 Ricky Ponting 47.28 Michael Clarke 44.89 Simon Katich 41.13 Adam Gilchrist 39.59 Shane Watson 34.66 Brad Haddin 30.60 James Hopes 28.00 Brett Lee 26.28 Damien Martyn 25.29