I have something like that.
Sicne the last update afew weeks ago, opera as turn sluggish. it takes like 3 to 4 seconds to open a new tab. In loading that tab it will take about abother 6 seconds. i dont know what the problem is, but am switching to chrome untill its fixed.
My computer specs are:
Intel Core i5-3570k
Ram: 16gb
GPU nvidia gtx 470
ssd 128Gb + HD 1Tb

Any help is apreciated.