I have same problem with a Lunatik Taktik Extreme case on my iPhone 5, just can't grab that **** bar. And to those who say its 'our fault' for buying a bulky case thats just rubbish, Firstly, the case is over $100 and I purchased it to guarantee protection of my phone so I will not simply not use it, second, these bigger protective cases were out prior to iOS 7 was released.
The top notifications bar works fine but grabbing the control centre is impossible. A few millimetres increase to the grab area would be perfect. Also to note as well is I get occasional lag when grabbing the bar without the case on.