Logging on October 14th from 4-7PM Eastern on PSN will earn you triple XP all weekend, which also applies to Xbox Live. However there's top swag.
For PlayStation 3 gamers you could win "one pair of individually-numbered, hand-painted limited edition PlayStation 3 controllers," reads the Rockstar newsletter. To enter for a chance to win them you need to visit the tomorrow.
There you need to "fill in your info under the 'Sweepstakes Entry' tab near the bottom of the page." It'll be open to competition entries from 3PM Eastern. For more info about the multiplayer event and the prizes to be had visit the official .