Opera 12.15+ (and later versions of 12.x) have worsened web-site compatibility. Security flaws (that were fixed in 12.15+) were extremely minor and insignificant.
So, use 12.14 (x86 or x64) for maximum compatibility.
Details: http://forums.opera.com/topic/550/prweb-crashes-opera
Thank you for sharing.
As you found in the another post, 12.16&12.17 x64 has serious JS compatibility issue. But they don't appear on other versions.
Before this, have been using 12.15 x86 for quite long time, and I have taken it as 12.16 till checked my server log UserAgent.
12.15 seems easy to crash or stop response, compatibility is indeed worse than 12.14, especially for some pop-up small window, there's usually nothing pup-ups.
Have just submitted bugs to Opera ASA about the 12.16&12.17 x64 issue today, not sure will they care.
It's not wise for Opera ASA to give up Presto, I don't think there's any company can work better on Blink core than Google.
I'll consider rolling back to 12.14 someday.
BTW, Is there any solution for default search engine reset bug for 12.14?