My suggestion is to not use custom UITableViewCells. I used to do it your way, but there's a much better way. Use the accessoryView property of the UITableViewCell, which you can assign an arbitrary view to, such as a UITextField or UISwitch. It shows up exactly as it would in the Settings application.
Then, when you need to access it, just use
NSString *text = ((UITextField *)cell.accessoryView).text;
However, you must be careful about setting up cells and accessing their values. If any cell goes offscreen, it will be removed and you will not be able to access the text field. What you want to do when setting up your cell is:
cell.accessoryView = nil; //Make sure any old accessory view isn't there.
if (/*cell needs text field*/) {
UITextField *textField = [[[UITextField alloc] initWithFrame:frame] autorelease];
textField.text = savedValue;
cell.accessoryView = textField;
[textField addTarget:self action:@selector(textChanged

forControlEvents:UIControlEventValueChanged];
}
...
- (void) textChanged

UITextField *)source {
self.savedValue = source.text;
}