This is THE MAJOR problem with Opera right now. I am filling up my download folder with useless files which I want to open instead of saving, and then save them if I like, in their proper folders (not in the download folder). This is also a bit of a security risk as some of these files were saved and had malware in them! EXE files show up in my download folder that I never decided to download - they just appeared (and Opera put them there). I am very careful about downloading ANYTHING, but it seems they were downloaded without me even knowing it was happening - or is was so fast that it was over before I could stop it. I need PDF's, Torrent files, DOCs, etc. to open in specific programs (where any suspicious files are dealt with). Also need to control EXE's etc, from finding there was in without my explicit permission. Pre-chrome Opera worked just fine with this.
I actually like this new Chrome version of Opera better overall. Though is was released as the main version WAY too early! In fact it probably still should be only a Beta as not all the functions are there yet.