Hi, welcome to the forums!
1) To the current users: How flexible is the engine?
We're designing Construct 2 to be suitable for any kind of 2D game.
s there any possiblity of scripting stuff?
Not directly, but you could try using the SDK.
) I know that it makes HTML5 games, but is it possible to export them as an executable file?
There's no official means to do this yet, but as you say, there are some tools/libraries around that just embed a browser window in to an EXE window. I still don't get why people want to do this though? Why not just let your game play in a browser rather than limiting it to the Windows platform and making the user go through a bunch of security warnings?
) Is there any way of using C2 with, let's say, Tiled (tileset editor) ?
Try using 'import sprite strip' in the animation frames bar to import grids of sprites as animation frames. Set the animation speed to 0 then you can use the sprite's 'initial frame' property to choose a tile. Enable snapping to grid in the View ribbon tab and use Tiled Backgrounds for large areas of repeated tiles. Yeah, it's not as easy as it could be, but it's something (of many things) to improve on our todo list.
) As a last request I'd like people to tell me why I should chose C2?
Well, if you ask me, I think it's simply the best game editor on the market! :)