Considering some of the suite upgrades I have gotten, I think its value is quite substantial.

On my next stay in Hong Kong alone I view my Diamond status as saving me thousands of dollars. I was originally planning to stay at the Four Seasons Hong Kong (in a room that would potentially upgrade to a suite), but could not bring myself to pass up the opportunity to use a suite upgrade at the GH. I realize that the two properties are not comparable per se, but I am very happy to be confirmed in a suite at the GH with grand club access at literally a fraction of what I would have otherwise paid.