Well, the Opgal device has a resolution of 384 x 288 while the E4 lists 80x60. It's probably worth the asking price.
The E4 can be modified for 320x240 support (at least the older ones could, don't know if they've "fixed" this or not), but it sounds like Opgal's sensor is even better in that respect.
That might be a dirt cheap way to get a passable IR cam.