Heh, just had an email from Mitch and he said it wheelies quite well
It may be the profile of the tyre - I was exactly the same when I bought the 748 second hand, as the previous owner had squared off the tyre quite badly and because of the steep transition from upright to leaned, it really did feel like it was falling into the corners and would have me off.
Once I'd changed the tyres (from Pirellis to my favoured Bridgestones) it felt 100 times better and didn't feel like it was going to let go at any minute.
So yes, get some new tyres on it as, if anything, it will give you confidence in your head.