We (me, DH, DD) have been at WDW for the last 2 NYEs. In 2004/5, we spent all day (starting with 8am Crystal Palace breakfast) at Magic Kingdom. The fireworks were wonderful, but the crowds were horrible. The area near Pirates and Jungle Cruise became an absolute bottleneck, especially when they started handing out noisemakers and hats. We managed to snag 3 curbside Main Street "seats" after dinner and spent most of our time being trampled by people who couldn't be bothered looking for the crosswalk and just had to step on us. The early part of the day was a lot of fun - but as the morning went on you could feel the park getting more and more claustrophobic. We heard that it had closed somewhere between 10 and 11 am. NYE was the worst crowds we experienced of our vacation - crowds large but otherwise manageable by getting there early, staggering mealtimes and using FastPass.
This year, we went to AK for morning and afternoon and then moved to Downtown Disney for Cirque (wow! amazing!) and then Beach Club/Cape May buffet for dinner - finished the evening off at our camper (Fort Wilderness). We could see most of the fireworks along the beach - what a welcome relief from last year. DD and I went to MK on Dec 30th for EMHs and saw the NY fireworks from the bridge. Wow!! We experienced the 360 show and everything. Not crowded, all of the music and Tinkerbell. Who could ask for more? That would be my recommendation .... avoid MK on NYE by experiencing the NYE magic the night before. Driving between AK and DTD, we saw the signs that MK and Epcot were closed. (During dinner, we heard a family saying that their plans had been ruined because they didn't get over to MK early enough and didn't want to go anywhere else.) We were really glad that we had opted for something a little different. Again this year, crowds were from Christmas Day on, but manageable if you got there early and used FastPass.
Enjoy!