Yes, I know how to do it on the command line. I also could install Filezilla. No problem.
I just wonder: Does KDE 4.3.4 really come without any graphical ftp/sftp client out of the box??
I for one liked the Nautilus where I could set up network connections and bookmark them. Dolphin doesn't seem to have that.
Should a file manager these days not offer file transfers out of the box? Or should I rather suggest this to the 'New Ideas'-forum?

And I did my homework here, and searched for 'ftp client'. There were some add-ons, some sourceforge programs, but no clear answer in the sense of 'yes, here it is and comes by default'.

All KDE applications support FTP natively, through KIO. Dolphin however does not make it easy to access, due to the "Breadcrumb" navigation.

Konqueror has an address bar, through which you can type ftp://<username>:<password>@<host>/<path>
Note that providing a username and password in the url isn't required, since it will ask for one if it is needed. ( ftp://<host>/<path )

I use dolphin all the time for ftp, once the address bar is changed to "editable location bar" it acts as a normal address bar.

Plus, using the "places" bar to store your connections makes things simple.

I tend to split the window and then open the connection in the right hand pane as below



Because of the native network transparency of KDE you get the best of both worlds.
The layout is fairly similar to most ftp clients and the files are seen and can be manipulated as easily as local ones.

Thank you logs_con for that hint