No FRI anymore.
If you accept the PA offer, your exit date is instantly moved to your 55th birthday. Therefore, to leave before 55 you must PVR and in doing so sacrifice about 10% of any pension rights you would have otherwise been entitled to.
Additionaly, your acceptance of PA ties you in to a non-negotiable 5year ROS from your original 16/38 point, not date of acceptance, despite not actually knowing under what terms of service (regarding pensions at least) you will be under post 2015. That same commitment used to be worth 80k under FRI 3.
The draw would be the knowledge that you won't be kicked out at the end of your existing engagement.That aside, I wouldn't touch it with a barge pole. Neither it would seem would most of the recipients of PA offers.
Good luck.