I have no doubt that she can sing, but I've yet to see her give a performance where she's singing in time to the music and has a real connection to what she's singing. I first noticed the lack of rhythm/timing on BGT. I thought it was something she'd get to grips with in time, then I saw a performance from her on TV this year (guest performance on BGT, I think...when she was singing a Madonna song) and she was still ignoring the tempo of the music and singing at her own speed.
I agree. This is where Emperors New Clothes comes in. If anyone else performed like this it would be deemed 'not very good' but it is just 'ignored' as it is unmentionable as you can't say that about Susan. The worst I saw was her attempting to do a duet with Elaine Paige - dear oh dear. I felt for Elaine trying to sustain the duet as Susan was oblivious to rhythm/timing.