From my one day of usage I have found WiFi has a nasty habit of crashing if you are getting a poor signal. It will still claiming to see the WiFi network (at least sometimes) but fail to connect to it.

This may be connected as its quite likely its crashed it will not enter power saving mode properly. Impossible for me to say from only a days use though, the battery is expected to only last 7 hours or so on its first couple of charges.