Definitely worth it. I made plat in Nov. When I traveled to Shanghai and stayed at St. Regis, I was given a junior suit two times (price difference was at least US$100). I also got the amenities+500 pts. At Westin, I was upgraded to a Crown Deluxe Suite. It's nicely decorated, and has a DVD player to boot. As a gold member (stayed 14 times in Regis this year), I was never upgraded to a suit. Okay, one time at Westin to Crown Deluxe, but it was because a very nice manager (and I begged/coerced him hehe). At Westin, I was given access to the lounge and breakfast. I brought an associate to the breakfast with no problem (I asked them). I dont think I would have these privileges if I'm only gold. In HK, I was given a harbour view room and access to the lounge.

If you can make plat, go for it. 25 stays a year is reasonable if you travel a lot. I split many stays to get more credits and I am glad I made it.