Not much. You can only switch from the $45/8G to this if:
1. your number is still in PM and got the text message today
2. you got the $45/8GB sim card but not yet activate it
I think some people who activated their card very recently (like 1 or 2 days top) but still yet to port their PM number might got lucky and got the new plan (or been offered for 1~2GB for dirt cheap on top of their $45 plan).