On the other hand, Davis' commitment to the issue of civil liberties should win him votes from the liberal bloc quite easily, and whilst I can't see him actively flaunting it, I suspect the party's remaining old school views on, say, Section 28, will disappear. I could be wrong, but I seem to remember Davis, unlike Cameron, voted for repeal. In addition to this, Davis hasn't got the curse of the "toff" background hanging around him.
On the negative side though, the fact he has been a frontbencher for some time, and lacks Cameron's youth and freshness may well enable Labour to continue to characterise their opponents as "same old Tories".
It could go either way, I think. Davis has very different strengths and weaknesses to Cameron. I suspect though, the UKIP vote would be much smaller, and Labour's inability to paint him as a toff would probably net Davis a small majority against Brown.