Labour normally has to be leading going into the official campaign period to actually have a chance at winning. This still looks unlikely. Remember - the Tories have been heavily targetting the marginals and can outspend all other parties easily these days. There are still no signs that swing voters (as a block) have been thinking about swinging back.
There has been a hardening of Labour support. Their 'retention' vote (ie how many of their 2005 voters will still vote for them) that was struggling in the 50's 60's has now reached about 70%. Prior to the recent bounce Labour never picked up voters from elsewhere; they are now picking up a small % of 2005 Lib Dem voters (who were probably Labour voters in 2001 etc)
The Tories, particularly in the 'how would you vote in your constituency' question are beginning to seep 5-6% to the Lib Dems; this may in fact be the beginning of a pre-election 'tactical drift' to the Lib Dems; it's bad news if they are drifting to the Lib Dems in Lib/Con marginals but good if they are moving to the Lib Dems in seats where the Tories don't have a chance.
All this will narrow the national gap between the parties but that doesn't necessarily mean that there is any change on the ground. Labour have also seen a firming of support in Scotland. The Toriy lead across England/Wales is a few points higher if you pull out Scotland; a rather infertile ground for the Tories.
It's also worth remembering is that there isn't much coming out from Brown Central or the Tories about the recent polls; no cofidence or lack thereof. It is probable that their internal polling is saying the same thing.
