"Also transfering files via USB is quicker than mtp isn't it? "
there is two options, mtp and usb mass storage(also called msc on some devices)
both work over usb port, both seems to be equally fast to me but msc gives more control i think, mtp on windows works weird i think, on linux supposedly there will be support soon but not yet
it is better not to mount the sd card on the pc, i had problems with the partition in the past and had to format the the microsd again, if your device doesn't have a microsd, only internal storage, then it could be different and couldn't tell if better of worse
"Like I said I have tried the Airdroid App and it works great with my windows laptop which is connected to my router via wireless. But my computer is wired to the router which somehow causes problems."
about accessing from the wired machine, i have done it and didn't found problems, what problems did you had?
what browser did you used? the app works only on chrome and firefox
"Plus Clementine can actualy mount the phone so it should be possible from Konsole?"
yes, the phone can be seen but the problem is that the mtp support is not what we need yet, and clementine will handle the phone as a mp3 player, and it isn't that
"Samba would be great as I have had experience with it hooking up to a windows laptop in the past. The thing is I don't know anything about rooting the phone and would prefer to find a method that avoids it for now."
rooting is the process of allow root access to apps on your android phone, it is done differently on each phone, some phones are simpler to root than others but there is lots of information about the process
in some models it requires to replace the firmware of the phone with another one, in others just edit a file, others just use a tool that changes a permission of a file, each model uses a different approach
for some brands that procedure will void warranty when you take it to service if it breaks, but other brands won't say anything about it
having said that, this is a video explaining how to do it on your phone
also a link for the processhttp://androidforums.com/one-x-plus-all-things-root/626339-one-x-plus-all-things-root-guide.html
in general, rooting has been a good experience on my xperia, especially with the android version i put on it and other things i changed
i am out of the warranty now, so i do what i want with it and when some part breaks i will fix it or get a new one