When DH and I had APs in 2006, we only made one rezzie ever for CRT... everything else was walk-up when we wandered through or rezzie for later in the day (we'd walk by at 4p and reserve for 6p)
We went to WDW in May this year unexpectedly (DH ended up in FL for three months and we met at WDW in the middle) and not only were 90% of the ADRs gone, but walk up was almost non-existent. We tried Garden Grill and were told we MIGHT be able to finagle something if we showed up at opening the next day and were willing to wait an hour. China, Japan, Norway, all booked. Mexico had limited walk-up, and when we called over to MK, nothing could guarantee anything and they said walk-up would be at least an hour if at all.
I was talking to my mom and she remembered how when she first went to EPCOT, you walked in, picked up a phone to an operator, made a dinner rezzie and went on your day. Now, it's plan 6 months out and hope it works.
I, personally, don't like dictating my schedule 6 months out -- we are more of a go with the flow group at the parks. We're planning on making three reservations for our trip next summer and just eat counter service if need be. I think it stinks - my in-laws have never been to Disney and would love to show them the great food but because they've never been, I think time is better spent enjoying the parks at our pace/decision rather than running from one ADR to the next.