This board is an example of how phpbb is not "slow". Look at the size of this board and how much traffic it gets on an hourly basis. A "slow" script couldn't handle it at all.
ok, you have now found out that phpbb is not a security risk, is not a bloated, slow script etc. etc.
Forget all the crap you read at those other boards and just get on with enjoying the best bulletin board script out there, free or paid.
( do I get any bertie points for that?