When I purchased the plan, I had to wait unitl the expiry of the current plan I was on. Then it was there the next day. Not sure maybe have to wait a little bit. You can also verify that you did in infact purchase it if you go to Payment History It...
It is faster.3-5mbps then 100mbsor less mbps on the new plan. Remember though Public Mobile is the lowest tier on the network. So speeds will vary at different times of the day I find.