Who do you think would have "control of the Senate" if Castle would have won? Certainly not conservatives and probably not even Republicans. Being beat over the head with Castle's liberal votes proving "bipartisanship" also would not have been "amusing".
Castle was not conservative, but he was from GOP and would have voted for GOP Senate Majority Leader (the most important vote) allowing GOP enormous amount of control. We would not have filibuster-proof control anyway.
Based on his earlier votes, he would have voted with GOP often (say, 40% of important votes, compared to Coons 0%). Scott Brown had already voted against GOP several times, but I still like him. Fred Thompson voted against conservatives several times with in your face attitude (free speech restrictions etc Centrist Coalition bs), but he was still better than Dem candidate.
DE is deep-blue state. Conservatives have little chance there, only outstanding candidates (say, Marco Rubio) would have any chance. Bad jokes like O’Donnell are losing by landslide.
And won’t Olympia Snowe and Susan Collins still have seats in the Senate? Not to mention Scott Brown and Lindsey Graham. So, control will be effectively Democratic for a while longer even if the Reps do win 10+ seats. The only difference will be who wields the gavel in the committees. This is not a trivial difference, but the rubber meets the road on the floor in the Senate. It’s in the House where committee chairmanship is vital.