Ok, this a summary of information from "reliable sources" we have today.
1. Photos of the wreckage
A missile explosion is very likely, very likely near the cockpit and likely on the left side.
Additional machine canon hits are unlikely, but cannot be excluded
2. Russian data
I would consider Russian data reliable. Though we are in a propaganda war, handing out fabrications to investigators would have been very likely and triumphantly exposed by the US. As nothing of that sort happened, I regard the US reaction as a silent confirmation. Later, I will talk about additional leaked US intelligence confirming this point.
Russian data tells us that
a. There has been another Ukrainian military plane in proximity of about 3-5 km
b. There were several Ukrainian BUKs in the area, radars were turned on, they were operative and had been moved close to rebel positions on the very day of the shoot-down and they were removed, when the satellite flew over again the next day.
c. That a US spy satellite, capable of providing high resolution images, was flying over the scene at the time of the shoot-down.
3. Eyewitnesses
Eyewitnesses may make errors and may not tell the truth. However, I would consider their report reliable, because it was presented on the BBC, which is not known to be biased in favour of Russia or the rebels, and because all witnesses tell the same story.
Eyewitnesses support 2a, that there was a military aircraft, probably below the airliner. None of the eyewitnesses reported an exhaust fume trail of a surface to air missile.
4. Physics
The rebel BUK site (Snizhne), as purported by the Telegraph and a US intelligence cartoon, was out of range of hitting or even discovering the approaching airplane.
Three Ukrainian BUK sites, however, were active and in range, and one of them (Shakhtar) appears to have been well positioned to shot down the airliner matching the wreckage profile.
https://docs.google.com/file/d/0ByibNV3SiUoobnpCVDduaHVORHM/edit?pli=1
5. US Intelligence Leak
US intelligence officers have leaked to Robert Parry, a US award winning investigative journalist, that
"What I’ve been told by one source, who has provided accurate information on similar matters in the past, is that U.S. intelligence agencies do have detailed satellite images of the likely missile battery that launched the fateful missile, but the battery appears to have been under the control of Ukrainian government troops dressed in what look like Ukrainian uniforms."
http://consortiumnews.com/2014/07/20/what-did-us-spy-satellites-see-in-ukraine/
Further,
"But I’m now told that U.S. intelligence analysts ... are concentrating on the scenario of a willful Ukrainian shoot-down of the plane, albeit possibly not knowing its actual identity."
http://consortiumnews.com/2014/08/03/flight-17-shoot-down-scenario-shifts/
6. US Data
Though the US is in a propaganda war and despite having pushed its allies into sanctions, the most drastic after the shoot-down, the US did not present any evidence to support their claims apart from social media information posted by unknown individuals with unknown background.
It is very likely that the US would have presented evidence to support their claims, that a). the airliner was shot down by rebels and b). the BUK was delivered to them by Russia, if they had such evidence.
It is therefore very likely that such evidence does not exist.
7. US History
In the 2 previous, most similar cases, the shoot-down of KAL007 by the Sovjets over Siberia and Iran Air 655 by the USS Vincences, we know that the US lied to the public.
a. In the case of KAL007 the US even altered the transcript of intercepted communication to produce the impression of a willful, murderous attack.
http://consortiumnews.com/2014/07/29/obama-should-release-ukraine-evidence/
b. In the case of Iran Air 655, the US lied about the circumstances of the shoot-down, that the captain ignored commands, chased Iranian small boats into Iranian waters and then unprovokedly fired on them and finally shot down the airplane in Iranian airspace on its regular route.
http://en.wikipedia.org/wiki/Iran_Air_Flight_655
c. Nine former US intelligence officers have signed a letter to president Obama stating that secretary Kerry was already not telling the truth to the public about the Sarin attack in Syria:
"We are hearing indirectly from some of our former colleagues that what Secretary Kerry is peddling does not square with the real intelligence."
http://consortiumnews.com/2014/07/29/obama-should-release-ukraine-evidence/
Summary:
All known facts from reliable sources indicate that the shoot-down was very likely committed by Ukrainian forces and that the US very likely knowns it. A willful attack is likely, as otherwise the deployment of Ukrainian BUKs in that area is hard to explain.