It's a good offer for the PRG. The standard offer is 25k MR for $2k MSR/3 months. However, the 50k MR/$2k MSR offer is fairly easy to pull via incognito or through VPN tricks. I pulled the same offer half a dozen times yesterday. Conventional wisdom is if you get the PRG, you will no longer be targeted for the 100k MR Platinum. Amex will have hooked you as a customer and you won't be on their radar for their best offers anymore. I've never received a 100k MR Platinum offer after getting the PRG (I didn't know!). I have been able to pull the 75k MR Platinum offer for myself and took it.
The PRG is a decent card with 2x MR at restaurants, grocery stores and gas stations, a $100 airline fee credit that's good for a $100 GC from AA or Southwest (or 2x $50 GC from Delta), 3x MR for flights booked directly with airlines, first year AF waived (but $195 AF after that). Bonus categories are nothing to knock your socks off, but the card's a moneymaker in its first year with the signup bonus, fee credit, and waived AF. But if you want to score the 100k MR Platinum one day, you may want to hold off on the PRG.