If I rename my computer by editing the
/etc/hostname file as shown here, will I get some synchronization problems with Ubuntu One, which knows my machine as a different name ?
Can I have any other problem I don't think of yet ?
No, the only problem will be that it will be still listed with the old name. If that inconsistency bothers you you can delete the token and re-sign in to the service.
Be carefull when changing the hostname, From the IRC #ubuntu channel factoid i quote:
Use hostname to set the hostname, or to do it permanently: edit /etc/hosts to include BOTH the old and new hostname and then change /etc/hostname to the new one.
WARNING! Make sure that your current hostname and /etc/hosts match, otherwise sudo may not work properly.
I have never had an issue with ubuntu one after changeing hostnames.