I have minimal contact with YC these days, and have no particular motivation to artificially inflate the value of the program.

YC was transformational for my company (MedCrypt). I have almost zero negative things to say about it, and would do it again immediately with my next company (despite probably not needing help raising the first $500k for a company).

I can't think of a situation where I would recommend a company not accept a spot in YC.