Short version:
Almost identical internally as the Remington Rayovac RMHL2AAA-B... same circuit board, battery holder, optic holder, and same tight angle optic... different mode sequence and lower LED bin, and doesn't have diffusers. The Remington is more robust, has more features, and is better.
Longer version:
Primus has a lineup of headlamps that hasn't been updated in 3 or more years it seems like. one good thing about this is that some of their headlamps periodically show up on eBay, Amazon, and other places at low prices.
the Primelite Eye and Primelite Power Eye have interested me for awhile because i've seen them for as low as $10 for the Eye and $20 for the Power Eye and also because they run on 2AAA, which is a format that i like. the only difference between the two models seems to be the color of the body and the output bin of the CREE XR-* LED, N4 for the Eye and P4 for the Power Eye.
i finally picked up a Eye recently when i found one for under $10. not being very popular here in the US, there aren't that many reviews on them, so i didn't really know much about them. when i received mine, i was a bit surprised by how the battery carrier looked identical to the one in the Remington RMHL2AAA-B. when i opened it up, i saw that the battery holder, circuit board, LED mount, optic retainer, and optic were exactly the same as the setup inside the Remington. some of the components on the circuit board are different which probably has to do with the mode sequence being different from the Remington (Remington goes short click for Off-High-Low-Off and double click at any point for Blink, Primus goes press and hold to go Off-Low then single click for Low-High-Blink-Off). otherwise, they are identical.
the output and tint aren't that bad considering the LED is a XR-C N4 WC. the beam is very tight as it is with the Remington, but not having a built-in diffuser really limits its usefulness. i don't really need a 30 lumen thrower for a headlamp. 100 lumen thrower? maybe. 30 lumen thrower? no.
i was also a bit disappointed with the build. the main body of the lamp and the battery door are held together by very thin, flimsy feeling plastic latches. worse, the design of the body and battery door make it such that the light is inoperable if the battery door breaks.
the best thing about the Eye is the headband. it is thick, has gripper strips on the inside, and has a tough feel to it like it was woven with a combo of elastic and cordura or something. i'm definitely scavenging the band and using it for a home made headlamp i'm building. i'm also going to scavenge the circuit board to replace the one in the Remington which i broke while doing a mod. the rest of the Eye will be used for spare parts.