A button to preview directly in node-webkit is really missed. Not a hard addition and great feature.
About the stereotypes...
The stereotypes will go away as soon as more and more 'desktop level games' made in C2 start to appear. I don't even mention mobile games. C2 needs more games like Iconoclasts which is brilliant and would never work in a touch screen (But in a console would). Mobile is not everything. Now that C2 has Desktop support there's no limit to the possibilities.
But there's complicating factors involved like the stereotype that web games are all simple mini games (Shame on me, my only game on Arcade is a mini dumb game :D). Until recently HTML5 platform was too immature to make big complex games but now it's finally ready. Or almost.
Another factor is that making games in pure JS is a terrible experience (Not everyone knows of C2 :D). C2 is here to save us all of that of course.
And another is that C2 is treated by many as a game maker for non programmers or entry level programmers (It's announced as such in fact, a mistake imo). The problem is that it attracts many people that are just starting , not exactly a bad thing, since there's many very talented amongst them, but scares away many experienced developers who are making those awesome 'desktop level' games in other engines.
Of course there's lot of pre-conceptions involved with web games etc. Those are still very hard to break. Flash is the culprit ! :D