With 80 types in my logbook, at-least half of which were P1, I still can't land a PC based flight sim.
So, no I don't think that they are all that realistic.
As to operating speeds for any common type, any qualified pilot is quite capable of finding enough information out from publically available sources far more accessible than a PC based flight simulator to fly and navigate most airliners. Apart from which speeds and procedures are kept on the flight deck anyway - it wouldn't be safe to rely upon memorised procedures.
It would be impossible to worldwide restrict access to flying training or aircraft information - the PC flight sim is an irrelevance in that respect. The only way, in my opinion, to stop terrorists doing undesirable things with aeroplanes is to stop them getting near the flight deck, or to solve the problems that make them terrorists. Given that in the past we've had terrorists trying to destroy free speech, freedom of religion - or trying to create free speech and freedom of religion, the latter probably ain't going to work.
G