I would say your chances are still pretty low... I live in ATL and rarely get the first class upgrade as a Platinum. The best benefit you will see is the SkyPriority treatment (special check-in area, security, earlier boarding).
Oh, and if you are flying SkyTeam metal internationally, you get to enjoy partner clubs. We just enjoyed time in the CDG Air France club while waiting for a regular economy ticket on Air France from CDG to TBS... As a Platinum, I was able to bring 1 free guest and just had to pay for our daugther. Great benefit if you travel internationally. I believe Golds get access, but you might have to pay for all guests. ($80/per)