From what I've read on here it seems to me that the only thing that has changed in 20 years of Gigs at Slane is the punters expectations.
The Buses and bars were a sham at REM in 1995 and they sound fairly disastrous for Oasis in 2009. Its possible to organise a successful event at SLane Castle, there were no complaints after the RCHP or U2 in previous years.
It must be noted that there was clearly a failure in crowd control, not only did people fear for their own safety whislt queuing to get in but the organisers were so concerned that they had to take action by stopping the scanning.
If half of what is on this thread and on Joe Duffy is true then I imagine it was a highly traumatic day for the organisers who may well have felt there was a near disaster on their on their hands. I'm hardly surprised that they have retreated into their shell declaring the event a stunning success (a mate of mine went in from the Navan side and whilst he didn't experience any of the problems others had he said the gig itself was disappointing) I would also expect them to improve next year simply because it obviously didn't work this year.