OP, I'm currently comp'ed Plat as part of the free targeted promo found elsewhere on FT and participating in that challenge and would opine that, if you plan on staying in the US and flying domestically over the next year, it's worth it.

As a 1W Sapphire, check the AC access parameters for that perk on domestic. AFAIK, Plat won't help there. IIRC, you should get access, something I as a domestic Plat do not, except if as part of an international trip or if a member.

100% RDM bonus - fast RDM builder

Access at booking to exit rows and MCE - big draw for me

Upgrades - got 20 with the promo and, as I've been flying paid F I haven't been using them; however, I've been holding phantom bookings on major routes close-in (within the Plat window) and finding the majority of them are clearing. Experiments on that parameter continue.

Plat status until end of February 2015. Nice perk of doing the challenge this time of year.

For myself, so far, it's been the RDM build which has been the most obvious perk. As I move back into economy flying, MCE/exit and upgrades will become more important. I've flown some inexpensive F tickets on necessary trips to save on flight time/miles since EQP's get a bump on F tickets to 1.5x versus .5x on the normal fares I fly.

Good luck.