I think people will find that the car is better than people think and LH will improve race by race.
The team spent far to long sticking to Kers while everyone else dropped it far earlier. THe car has speed but anyone can see LH slipping around corners all year long, he simply has no downforce. The biggest difference between kers/non kers is being able to distribute that 50kg in weight where its needed.
Give it a few races for McClaren to practice/test/race with new weight distribution and find ways to increase downforce and optimise for non KERS setup and I think they'll improve, a lot. You've also to a certain degree got to give the drivers time to adjust. For what 7 races LH had to ease off in the corners so as not to, die, and press the button down the straights. AS the car gets better, grip comes back they have to get back to racing the corners.
You've got to remember, he was always a VERY agressive driver and run the car ragged through corners. As the car gets more grip and he gets better at handling the corners, that aggressiveness will start to gain that time he used to have over other drivers in the harder corners.