There have been some other threads about this. Alan Ross did a review in View Camera Magazine. I think it was last year.
I have emailed Calumet and they tell me that the light source is now adapatble to Beseler 4x5 enlargers and available (rather than indefinite back order). However, I am happy enough with my Beseler 45 S dichroic light source for now. I too am waiting to hear more from early users before spending $1500 on one.
Kienzle also makes an LED light source but I have found it impossible to get much info in understandable English.