I'll second Jonathan99's remark about the battery life being non-existent. At the end of the day, after minimal usage, the battery's at the half-way point. Additionally, I've found that both the AC and Car chargers for the HTC S620 (T-Mobile Dash) work for the device, which was nice.
SAO, I think Wifi is coming on because the device can't get to the Internet through the cell module. At least, I'm pretty sure it is for me. I have a dead spot in my house that I've never seen any phone receive signal in, but the 503G responds by turning on Wifi to sync up with Exchange ActiveSync instead of just puttering around with no signal like every other phone. While that's a nice feature in theory, it annihilates the battery - even if we were given an option to turn that convenience feature off that would be nice because I for one hate it. Wifi is one of the few things I'd like to turn on and off explicitly.
No wireless feature should ever switch on by itself without your explicit authorisation. Not by default, anyway.
If you get on a plane, you need to be able to guarantee that all wireless facilities are switched off. If there's a chance that your phone may activate itself in the air, you shouldn't take it on the plane at all. Or you should remove the battery before boarding.