I'll be flying to Manila via Doha shortly, the flights seem to be over Syria and Iraq.
They do this many times a day, so I suppose it's pot luck (or lack of) that your aircraft is targeted.....

I'm taking my chance.

It is very considerably safer to fly now than it was a week ago. Whoever owned the equipment and whoever pushed the button - will not want the world on their backs a second time.

That is, as yet, unproven. Almost 3 weeks before the MH 777 was brought down, rebels were tweeting about having captured Buk missiles and launchers from a Ukrainian air force base.

These questions are asked sometimes of African Airlines, where the standard differs more. In Nigeria, these are some of the issues that have led to Arik acquiring vast market share over the last few years. It is also why some people prefer to go with branded quality airlines, rather than with more sketchy history.

If the "Islamic State" (pka ISIS) had previously credibly claimed to have SA-11 missiles, and were shooting down planes in that area, I would say you were incredibly stupid. They haven't though, so you are pretty much okay. Any substantive changes in military capability, impacting flights at cruising altitude and at 10,000 feet should be immediately assessed. This is bread and butter for an organisation like "Control Risks Group".