I've never not batch sparged. When I started all grain brewing, I batch sparged because it was easy. For the first few batches, I hit my numbers pretty well. I figured why spend money and time if this method is getting me to where I need to go. Don't fix something that isn't broke. I get about 70% efficiency, and I'm usually within my target gravity by +\- .002, which at this point in my brewing career is good enough for me.