I dunno about a prize but he'll almost certainly get more votes. Whether they count for anything is still unknown.
From what I've heard, the first few percentage swing points towards the Lib Dems will actually help Labour, as they'll be from Tory seats. As the swing becomes more pronounced, the model says that Labour will start worrying, places like Liverpool which are historic Labour safe seats are suddenly under threat.
Even with that though, unless its some monumental shift, the 'best' result for the Lib Dems will be a hung parliament. In that case, Brown stays on as Prime Minister and is given the chance to try and construct a government, likely by forming agreements with other parties. You saw that last night with the obvious difference in Brown's stance between Cameron and Clegg, he was effectively wooing Clegg in comparison.
I already know that my vote won't count though. I'm voting Lib Dem, but in a Tory majority of over 10k, that would have to be some serious swing to cause a change.