Charged mine yesterday, left it on for the last 18 hours - no SIM, no GPS, barometer app running. Battery now down to 42%. Of the capacity used, the barometer app has used 43%, mobile standby, idle & WiFi 12% each, display 1%. I'm a wee bit disappointed by that performance.
The back is held on by 6 tiny screws that are either Allen or Torx - can't see clearly - so battery changes in the dark & wet are probably out.
Otherwise: the display is good without being world-shattering, and the size is great for eBooks. The buttons are nice and positive. The lids over the ports are a wee bit fiddly, but then they always are. The earphone/hands-off-kit socket is under a lid, so if you want to ride in the rain while nattering with the missus you'll need to put the phone in a polybag.
When you power up at first it offers to install a bunch of "default apps". I did, then spent 10 minutes deleting ads for ski resorts. About half the 39 it sucked in were adverts or very limited test versions. Advice: don't.
That's it so far. Haven't tried it with a SIM yet 'cos of microsim etc.