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I think thats the issue with it and sometimes no matter how good it is, it just dont jell with people.
I know, this is because Opera used to have ads or to be paid, and people got angry at Opera. Their image of evil company has stuck and if there's a browser to hate, no matter how good it is, it's Opera. There's nothing Opera can do at this time. It's a brand recognition problem.
The themes are dull
The themes were dull. Now Opera has native OS integration and you can use skins submitted by users. You can have Opera look like Safari or IE for instance
way to many options
These options are hidden, and shouldn't annoy the average user. And they are essential for power user. Having them out of the box is better than having to go to a web site to download extensions that not always work across upgrades.
lacking linux support
What is missing exactly? I'm using Opera on Linux and it's worked great so far.
You can throw all the innovation and features into Opera but if people just dont like there's not much you can do.
Sadly, this is true.
To speak to OS integration, I use Opera precisely because if fits perfectly into my KDE desktop, right down to correctly inheriting transparent menus. I find the user interface to be perfect. The only down side is stability. It crashes more than all the other browsers I use. To rate them from most to least stable:
So while I continue to user Opera due to its perfect integration with KDE and superior features to Konqueror, I sometimes switch to Firefox when Opera crashes.