i've got one UITextfield:
textField = [[UITextField alloc] initWithFrame:CGRectMake(20, 10, 200, 33)];
[textField setFont:[UIFont fontWithName:@"Helvetica Neue Regular" size:14]] ;
[textField setDelegate:self];
Below you can see textfield on iOS 6.0 and iOS 5.1.


Why on 5.1 text it's bigger? In setFont size is 14.