My battery life has gotten a lot better now that I've finished Angry Birds Star Wars
Seriously though, games really seem to kill it fast - but nothing else makes a big hit. I remember on my HD7 just making a big download, whether over a data connection or wifi, would drain the battery by a noticeable amount. Yesterday my phone - albeit with limited use - was still on 60% or so after 12 hours discharge, with another 21 hours remaining according to Battery Saver. That's with a couple of background apps, NFC on, an hour or so of music playing (not streaming though,) and occasional checking of People hub and my RSS reader. Oh, and Facebook Chat switched on - I seemed to notice it made a difference to battery life on my HD7; not so much on the 8X. This is on o2 UK in London, so mostly H and H+ except for on the tube of course.
Overall I'm actually happy with my battery life now! A far cry from last week where it would struggle to last a day.
Also, I'd like to get a myth debunked here - I have heard from many sources that the new style of batteries we have in our phones do not need to be fully discharged and recharged to get the most out of them; in fact I have heard that letting them get down to critical levels regularly is actually detrimental to their life; the best policy is to top them up and keep them topped up. A half-discharge and full charge, or putting it on charge when it is 80% full, no longer decreases battery life. Who here with more brains (or links to websites with brains!) can confirm this? Anecdotal evidence in my case supports this - I've been charging my 8X very irregularly, and as can be seen above it seems to be doing fine.
EDIT:
this link looks like heavy going but has some good tips - they seem to confirm that Li-ion batteries don't have a "memory" which is affected by fully discharging.