Just got back from a trip to the MGM Grand over 4/22-4/25 on a comped room. I'm an mLife gold, bet around $100/hand ~4 hrs day, and figured I'd share a bit on the new "benefits":
1. Room upgrade - no upgrade available on check-in. Go figure : (
2. Access to clubs/VIP pool area (Wet Republic) - as noted in prior posts, whoop de doo. I was offered free admission to the clubs and VIP pool area. I agree with gengar, a "total farce."

At the end of my stay, I was unpleasantly surprised to find that my comps were SUBSTANTIALLY reduced from prior trips. The host explanation: "your comps were reduced since the new express comps offer you more freedom to comp yourself". My usual offer would be room and generally $300-500 of food/bev, depending on how many hours I play (varies based on win/loss). This trip, my comps, including express comps, were ~$170. It seems the fancy cards are the only new benefit of mLife.