Just picked up my E5.
Opened it, tested it, and then of course, took it apart.
Unlike the E3, it's pretty easy to open and totally non-destructive, which I guess opens the door for mods and such.
Have some pics, click to enlarge.
An unsuspecting E5.

Take off the screw and the clip pops off.

Press the white plastic 'tabs' and slide it out.

Board and holder, top side.

Bottom.

What we have so far.

Closer inspection.

Without battery.

Opamp is OPA2338UA, quick search on the other IC's didn't reveal much.
Also, is it me or does the opamp seems like it was hand-soldered or reworked?

Other angle.

After putting it back, I've been listening to it and compared to the E3 the most noticeable is less hissing.
I don't hear much difference in SQ, but I've only listened for 10min or so. Still pairs pretty well with my er4p.
Basically it seems to be a more practical E3, which is pretty good for the price.