Yes, I have, but not camping at the summit. There are several campsites on Winter Creek and Sturdevant Creek that are free and first-come, first-serve. They have picnic tables and fire rings. They aren't the most “wild” places to camp, but it can be a lot of fun.
I agree with Jeff. Summit no good. I've camped at Sturdevant Creek, great site if you can scout a place on the top it's away from where most people camp. Great place to hammock it up for the night. Basically if you do the loop clockwise, hit the peak, hick down to the camp, and then you can check out the falls in the morning before heading back to the parking lot. Up that wonderful long road. Or you can do the loop counterclock-wise and camp at winter creek camp, and then the next morning head to the parking lot that works too but makes the next day pretty uneventful.
We did the hike this past Monday jan 28. It is open for now, but theres going to be rain on thurs. It helped now that the Government is open, for the roads to open up. it was great weather and the trails are in good condition, the camp sites we passed looked in good condition to camp. Just be advised for the coming weather this thursday
I talked to the rangers and in Angeles National Forest you can camp anywhere you want as long as you are 150 yards from the trail, from water, or any structures. And you must get a fire permit even to use a backpacking stove. Hope this helps.