We just got back from WDW on 4/11 (we were there from 4/2 thru 4/11). We did have a GAC for DD, but only needed to use it twice. In general, if the regular line is 20 minutes or less, the GAC is not needed.
We found that some things with long lines earlier in the day, got much shorter as the day went on. In fact, the on Sunday (our next to last day) we went to AK. The Safari was no wait for people without special needs. We had to wait for about 15-20 minutes, but only because DD can't transfer. For the Lion King and Pocohontas shows, we had no wait. Lion King was not full. The rest of us didn't want to get wet, but DH went on Kali River Rapids twice, basically as fast as he could walk on. While he did that, the rest of us went on the Maharajah Jungle Trek (where we could sometimes not even see anyone else).
We had pretty much of the same experiences at other parks with waiting.