I actually got comped to Plat a few years ago. Essentially all my stays were in CYs and FIs and, other than the plat arrival gift and maybe my name on the daily Welcome board, nothing much different.

But ...

My whole purpose in getting the Marriott points was so that I could take nice vacations in Europe, and there it absolutely makes a big difference. Unfortunately, I've had no stays in the past two years, so Marriott let me keep Plat for one year and then gently dropped my to Gold this year. That was enough.

We recently had a trip to France/UK, and my Gold status got us everything we wanted at the Marriott in Monaco and full breakfast/CL admission at the Heathrow Marriott, so I'd say it was certainly worth it for me.

As others have pointed out, it depends on where you stay. If you frequent FS marriotts and like nice props ex-US, I'd go for it. If you're mainly a CY/FI guy and have no exotic vacation plans, let it happen with the rollover.