I was there last week and rode it first thing Thursday morning and I can tell you it was definitely in technical rehearsal at that time. There were quite a few glitches but once the ride finally started it was awesome.
The people right in front of us were saying they rode it Wednesday night and waited in line almost an hour and a half and then it broke while they were on it and they had to wait a little while to be let off. I know when I went Tuesday (April 22) I didn't really notice it but my husband said, hey, didn't there used to be pictures on that wall? Sure enough, all the Simpsons graphics were gone but the fence was still there. Then Wednesday I noticed the fence had been taken down but all the attendants would say is "All I can tell you is, it's not open right now." Then a little while later a line started but they weren't letting anyone in and still saying all they could say is it wasn't open right now. I don't know how long those people stood in line but I would never stand in line for something I wasn't even sure was going to open.
There were several glitches, though, and I would be surprised if it was officially up and running this soon after that. Technical rehearsal, most likely!