Gibbie I am currently testing an X8 which I got on Tuesday. I had an old pay as you go sim in it with only a small amount of credit so I turned off data traffic and just used my home wifi to do the set up and downloading of apps etc. I finally had to charge the phone on Friday afternoon.
Yesterday I put my contract sim from my X10 in it with data switched on and had to put it on charge last night, Saturday as I went off to bed. I would expect to have to charge it nightly on my general use, if you use your phone loads then you will deplete the battery sooner. I would give it a week or so of charge and discharge to see if it gets better over time.
You could turn down your polling times for Facebook / Twitter / Email to just hourly or set them up to manually update when you go in to the app. That helps with battery life too.