It depends on who you talk to, and what you are willing to believe. For those who see conspiracy lurking around every corner, and 'live' in a world filled with James Bond intrigues, no 'official' word or refutation would be viewed as un-tainted by a 'cover up'. Even my own opinion would be taken as evidence that astronomers know the full story but are stonewalling or trying to abet the US government in covering up this alleged crash landing. I think you should look very carefully at what the proponents of such a landing have to gain by proposing that some grand conspiracy is afoot. It is easy to say the government is trying to cover up the evidence, because EVERYONE knows that any government is completely unable to fully defend itself against such an accusation. And when they do present the evidence as it exists, if the evidence isn't exactly what the crash landing proponents want to see, they will again claim the government is not coming clean with the evidence.
Personally, my opinion is that nothing happened of any consequence. I think that just as soon as you start to get people's emotions involved in any discussion, you are no longer dealing with what is actually occurring, but with what some people want very desperately to be true for their own personal reasons. As someone who spends their entire DAY studying the physical world, and someone who does this day after day, week after week for many years, I find it very hard to accept any of the evidence the proponents of the Roswell 'incident' have to offer. For many people, that makes me a narrow minded scientist; which is a very very common attack made against scientists.
You should remember, however, that scientists are the same people who gave you the unimaginably weird world of the quantum, the odd laws of special relativity, the curved space of general relativity, and the ability to reconstruct the first minutes after the Big Bang. Compared to this, alien civilizations visiting Earth is child's play!