The font is very small and hard for some to read so I'd like to make it closer to the font size used on the buttons below it.
You can change font property after show method(like showFromBarButtonItem) as below.
CGRect oldFrame = [(UILabel*)[[sheet subviews] objectAtIndex:0] frame];
UILabel *newTitle = [[[UILabel alloc] initWithFrame:oldFrame] autorelease];
newTitle.font = [UIFont boldSystemFontOfSize:17];
newTitle.textAlignment = UITextAlignmentCenter;
newTitle.backgroundColor = [UIColor clearColor];
newTitle.textColor = [UIColor whiteColor];
newTitle.text = @"My Title";
[sheet addSubview:newTitle];
[sheet release];