Because I'm bored....
Davis-as-leader would be very different from Cameron; most noticeably all the early repositioning of the 2005-2007 period would go out of the window. Davis wouldn't go for anything like 'hug a hoodie', nor would he be particularly interested in Green issues. Davis would instead try and ape John McCain-style positioning (I use him because he's the best example) attacking Blair strongly, very strongly, on issues of trust and basic standards in public life, and, above all, ID cards and the size of the state. Davis would try to broaden the social appeal of the Tories slightly by reaching out on the issues of things like inner cities, single mothers etc, but at the same time stressing obedience to traditional Tory policies particularly on crime and especially public finances. Other 'big' issues of the last eight years such as immigration and social conservatism would be put on the back burner. Davis would take a completely purist eurosceptic line but again, wouldn't stress it as a main issue.
But this wouldn't go down particularly well with most, and he would have strong rumblings from the left and the press. Davis will not be in particularly good shape by the time Blair retires. (Assuming that goes as per OTL) There will be murmurings of a leadership challenge 'if things don't improve.'
A possible POD here may be in what happens to Davis Milliband. In 2007 OTL Milliband was seen as the great white hope who the Blairites wanted to run against Brown, in order to take on Cameron. Here that will not be half as pronounced as in OTL, as there is no 'Tory Blair'. In consequence Milliband's prospects won't be talked up; he is unlikely to get the FCO as his reward which means a different cabinet lineup. Brown is probably more secure in his cabinet, and probably won't feel the need to make much of an accomodation with the Blairites. The big 'if' depends on whether or not Brown will go for the 2007 election here or not. With Davis not in as good shape as Cameron he may well do. In which case, thing will be very dicey for Davis. He will very likely lose the election to Brown.
If not, then 2007-2008 is going to be a smoother ride for Davis than the last few years, as Brown starts to implode. Although the media would still be annoyed, as they would view Davis-Brown as a step back to Smith-Major, and you would hear the old complaint that 'it will be our bank manager versus their bank manager' again. The press in particular will want to make mischief at the 'boring' leaders and will be aching for something 'interesting.' This will fuel criticsm of Davis.
But then 2008-2009 comes around and Davis starts coming into his own. His previous warnings about financial rectitude, public trust, reforming government, and the size of the state would begin to look completely prescient, even though he has followed an embarrasingly strong deregulation line. If Cameron gets Treasury in 2005 then Davis will probably dump him from that soon after the crisis hits, put him into the education brief, and bring in a heavy hitter to shadow Darling/whoever. (NOT Clarke) All the previous criticsms about Davis not being 'fresh' enough would melt away, as the need for an experienced team above all else hits the public and media, and Davis would be hammering Brown on the issues. His shadow cabinet would look very much like a government in waiting, and Tory supporters and activists are much more enthused about the party than in OTL. By this time in the alt-TL, Davis is running an election-winning if not world-beating lead in the polls and people are looking forward to the general election.
Shadow Cabinet would look something like:
Leader - Davis
Treasury - Hague
Foreign Affairs - Rifkind
Home Affairs - Grieve? Lansley?
Education - Cameron
Health - Letwin?
Defence - Fox
etc
