well heres my take for what's it's worth, which isn't much lol. We stayed at RPR for one night last November and then Holiday Inn across the street from universal for another 2 nights. We went to early entry one morning during that time.
All onsite hotels were pretty booked up, there had been a hurricane earlier in October that cancelled two of the Halloween nights and they ended up rescheduling them for the first weekend in November which is when we were there, not sure if that had anything to do with the hotels being booked up or what.
We got to the park right at opening at 8 am, walked straight back to Diagon Alley and found the line for Gringotts lined all the way to the entrance of Diagon Alley. I'm not kidding, the line ended in front of weasleys wizards wheezes. We opted not to get in that ridiculous line and walked around a bit instead.
Then we went out at 8:40 to head to the train station, there was a huge crowd standing in a big semicircle round the entrance with employees trying to keep them back. We all stood there in a big cluster until about 9:10 when they finally announced that there were technical difficulties and the train would not be operating for some time.
All in all, EE was a big waste for us, not worth it even in the slightest. express passes for the rest of the parks made it worthwhile for the onsite hotel though for the one night.
My next trip we are doing RPR again for one night for the express passes, and this time EE is at IOA. We may get up early for it just to see an uncrowded hogsmeade. If you want to ride the rides, I'd be out front of the parks at least a half hour before EE starts IMO, too may hotel guests for too few rides open at that time of day.